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International Household Survey Network

IHSN

Quick Reference Guide for Data Archivists

DRAFT - Version 2019 -04

Content

Introduction 1

1. Gathering and preparing the data set 2

2. Gathering and preparing the documentation 5

3. Importing data and establishing relationships 5

4. Importing external resources 8

5. Completing metadata 9

5.1. Good practices for completing the Document Description 10

5.2. Good practices for completing the Study Description 11

5.3. Good practices for completing the File Description 23

5.4. Good practices for completing the Variables Description 24

5.5. Good practices for completing the External Resources description 28

6. Creating variable groups 29

7. Running validations and diagnostics 30

8. Generating the survey documentation in PDF 31

9. Independent quality review 32

Introduction

This Quick Reference Guide for Data Archivists provides data archivists with guidelines to document a micro-dataset in compliance with the Data Documentation Initiative (DDI) and the Dublin Core (DCMI) metadata standards, using the World Bank Metadata Editor.

The World Bank Metadata Editor is an application designed to help document data collection operations undertaken for different kinds of research projects. The application is developed as an open-source tool by the World Bank. A number of Metadata standards recognized as global models for defining and describing different types of data have been integrated into the Metadata Editor, these are: The Data Documentation Initiative (DDI Codebook), The Dublin Core Metadata Initiative (DCMI) and the ISO 19139 for geospatial data.

The Metadata Editor is modelled on the Nesstar Publisher. As such it should provide a familiar environment for the Nesstar users. As an added benefit, the Metadata Editor is flexible and can support the documentation of multiple-data types. Out of the box it supports the documentation of survey data, time Series data, geospatial data, statistical tables, images, analytical scripts and standalone publications or documents.

This Guide summarizes the process in 10 chronological steps:

  1. Gathering and preparing the data set
  2. Gathering and preparing the documentation
  3. Importing data and establishing relationships
  4. Importing external resources
  5. Adding metadata
  6. Creating variable groups (optional)
  7. Running diagnostics
  8. Generating the standard survey documentation using the PDF generator
  9. Quality assessment
  10. Producing the output for publication

Also provided (in appendix) is the IHSN DDI Reviewers’ Feedback Form which provides a standard tool for the assessment of survey metadata by an external reviewer.

This Guide is not a Metadata Editor reference or training manual. It is assumed that users are already familiar with the Editor. A Metadata Editor User’s Guide is available at https://metadata-editor.readthedocs.io/en/latest/.

Before you start: organizing your files

Documentation of a dataset will be most efficient if you organize your data and other files properly. We recommend that, before anything else, you create the necessary directories as follows:

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  • Create a directory for the survey. We suggest you name it using the

    country, survey’s year and the abbreviated name, e.g. “UGA_2018_HIES”

    for “Household Income and Expenditure Survey” of Uganda collected in 2018.

  • Create various sub-directories for the. data files (and for the various versions of the dataset if relevant)
  • Create sub-directories for the documentation and for the program files if relevant (see example).

1. Gathering and preparing the data set

Gathering and preparing data is a process that requires great care. Prior to documenting a dataset, it is important to ensure that you are working with the most appropriate version of all the concerned data files. If the dataset is meant for public release, one should work with the final, edited, anonymous version of the dataset. If the dataset is being documented for archiving and internal use only, one may include the raw data as well as the final, fully edited files. The Metadata Editor provides you with the possibility of documenting the specificity of each version of the dataset.

Much of the quality of the output generated by the Editor will depend upon the prior preparatory work. Although the Editor can make some changes to the data, it is highly recommended that the necessary checks and changes be made in advance using a statistical package and a script. This ensures accurate and replicable results.

This section describes the various checks and balances involved in the data preparation process, such as: making a diagnostic on the structure of your data, cleaning it and identifying the various variables at the outset. Listed below are some common data problems that users encounter:

  • Absence of variables that uniquely identify each record of the dataset
  • Duplicate observations
  • Errors from merging multiple datasets
  • Encountering incomplete data when comparing the content of the data files with the original survey questionnaire
  • Unlabelled data
  • Variables with missing values
  • Unnecessary or temporary variables in the data files
  • Data with sensitive information or direct identifiers

Some practical examples using a statistical package are provided in Section A “Data Validations in Stata: Practical Examples.

Note

If you are working in a data archive, be careful not to overwrite your original variables. Since managing databases involves several data-checking procedures, archive a new version in addition to the original. Work on this new version, leaving the original data files untouched.

The following procedures are recommended for preparing your dataset(s):

1.2. Data files should be organized in a hierarchical format

Look at your data and visualize it to understand its structure. It is preferable to organize your files in a hierarchical format instead of a flat format. In a hierarchical format, columns contain specific information about all possible units of analysis and rows form the individual observations (households, establishments, products, communities/countries, or any combination of those). Hierarchical files are easier to analyse, as they contain fewer columns that store the same information and are more compact. A flat format contains multiple columns with information on only one specific unit of analysis, so the information becomes redundant. For example, the information provided in one column is about the household head, and the row provides information on the child in the household.

Table 1. Flat Format

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Table 2. Hierarchical Format

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Tables 1 and 2 illustrate the two data structures. They contain the same information about six people on age and their relationship with the head of the household. The flat dataset (Table 1) stores the information on each family member in a new column. Note that for every additional member or characteristic, the dataset gets flatter and wider. The hierarchical dataset (see Table 2) has one observation and one row per person. Each variable contains a value that measures the same attribute across people and each record contains all values measured on the same person across variables. For every additional member characteristic, the dataset maintains the same number of columns, gains additional rows and gets longer and less flat compared to Table 1. The first two columns of this dataset have a hierarchical structure, where the ID member column is nested inside the ID household column.

Hierarchical files are easier to manage. Suppose in this example that there were many characteristics measured for everyone, the hierarchical structure would be a more convenient format because for each new characteristic, the dataset creates only one additional column, whereas, in the flat structure, it would create as many columns as there are people in the data with such characteristics.

1.2. Datasets with multiple units of analysis should be stored in different data files

It is recommended that you store your data in different files when you have multiple observational units. For example, Table 3 shows a dataset that has both household-level data (columns on the type of dwelling and walls material) and individual-level data (columns on the marital status, work status, and worker category). Note that storing both levels of information in one dataset will result in a repetition of household characteristics for each household member. In Table 3, the information about the columns ‘type of dwelling’ and ‘wall material’ is repeated for everyone. Sometimes, this duplication is inefficient, and it is easier to have the dataset broken down by observational unit, into multiple files. In this example, it would be simpler to create two files: one for the household characteristics and another for the individual characteristics. The two files can be connected through a unique identifier, which in this case will be the household ID and member ID. We discuss the need for this unique identifier further on in this text as well.

Table 3. Single data set with more than one observational unit

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1.3. Columns in a dataset should represent variables, not values

It is recommended that columns represent variables (e.g., sex, age, marital status) and rows represent observations (e.g., individuals, households, firms, products and so forth). In some datasets, columns instead of describing variables or attributes, describe values, which means that one variable is broken into segments and each one is stored in different columns. While this dataset structure can be useful for some analysis, the standard data structure where columns are variables and not values is the norm.

For example, Table 4 (options 1 and 2) gives information at the individual-level on marital status, relationship with the head of the household and age. The difference between both tables is how the variable ‘age’ is reported. Option 1 had broken the variable ‘age’ into segments. This practice makes your data: i) messier, it has values of the variable as headings, and ii) inefficient, it increases the size of the dataset. Option 2 is recommended since there is only one heading and store of the information occupies less space, allowing the user to identify the structure of the data in a clear manner.

Table 4. Data Structures: Hypothetical datasets

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1.4. Each observation in every file must have a unique identifier

Before you check for uniqueness of the identifiers in your files, you need to figure out the unit of analysis. Even if you are not the data producer, it is often easy to identify it. You can always review the documentation to see if the information has been provided. Below, some examples of units of analysis:

Table 5. Unit of Analysis by Study type

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Once you recognize the unit of analysis, the next step is to identify the column that uniquely identifies each record. If a dataset contains multiple related files, each record in every file must have a unique identifier. The data producer can also choose multiple variables to define a unique identifier. In that case, more than one column in a dataset is used to guarantee uniqueness. These identifiers are also called key variables or ID variables. The variable(s) should not contain missing values or have any duplicates. They are used by statistical packages such as SPSS, R or Stata when data files need to be merged for analysis

The absence of a unique identifier is a data quality issue, so one needs to ensure that the unique IDs remain fixed/present during the data cleaning process. If this correction is not possible, the archivist should note the anomalies in the documentation process.

Best Practices

  • It is recommended that ID variables be defined as a numeric since sorting and filtering records is much more efficient when variables are numeric.
  • ID variables should not contain spaces, special characters or accents, since they may suffer modifications when the dataset is converted in different formats.
  • For the convenience of users of the data, avoid identifiers consisting of too many variables. For example, in a household survey, the household identifier should ideally be a single variable (which you may create by concatenating a group of variables [3]), and the individual identifier should be the combination of only two variables (the household ID, and the sequential number of each member).
  • It is recommended that you generate an ID based on a sequential number, however, keep in mind that it should not be too long because statistical packages and spreadsheet programs store a number of digits of precision, so opening a data set that contains ID variables with many characters, might result in truncated fields. For instance, the limit of the number of characters in Microsoft Excel is 15, so it changes any digits past the fifteenth place to zeroes.
  • If you prepare your data files for public dissemination, it may be preferable to generate a unique household identification that would not be a compilation of geographic codes (because geographic codes are highly identifying). This recommendation is to ensure anonymity and will be explained in further detail later on in this text. The following example shows how to construct a unique identifier without using detailed information provided by the geographic codes.
Example
  • Suppose the unique identification of a household is a combination of of variables PROV (Province), DIST (District), EA (Enumeration Area), HHNUM (Household Number). Options 2 and 3 are recommended. Note that if option 3 is chosen, it is crucial o preserve (but not distribute) a file that would provide the mapping between the original codes and the new HHID.
Option 1: Use a combination of
four variables
Option 2: Generate a
concatenated ID
Option 3: Generate a
sequential number
PROV DIST EA HHNUM HHID HHID
12 01 014 004 1201014004 1
12 01 015 001 1201015001 2
13 07 008 112 1307008112 3
Etc Etc Etc Etc Etc Etc

Once you recognize the unit of analysis and the variable that uniquely identifies it, the following checks are suggested:

  • Even if the data set has a variable with a label “unique identifier”, it is important to confirm that this variable truly does uniquely identify each record. To confirm or even to find out what the unique identifier is, you can make use of the -duplicate- function in SPSS or the -isid- command in Stata (for R, do as shown in Table 6). For more details, refer to Example 1 and Example 2 of Section A.

Table 6. Check for unique identifiers: STATA/R/SPSS Commands

STATA Code R Code SPSS Function

use “household.dta”

isid “key1” “key2”

my_data<- read_dta(“household.dta”)

id <-c( “key1” , ” key2”)

isid(my_data, id, verbose = FALSE)

GET FILE=’household.sav’

execute.

From the menu choose:

  • Data>Indentify Duplicate Cases
  • Select Key Variables
  • Finally, check that the ID variable for the unit of observation doesn’t have missing or assigned zero/null values. Ensure that the datasets are sorted and arranged by their unique identifiers.

Table 7 below gives a hypothetical example. In this dataset, the highlighted columns (hh1, hh2, hh3) are the key variables, which means that they are supposed to make up the unique identifier. However, looking at those variables, we can identify some problems: the key variables do not uniquely identify each observation as they have the same values in rows 4 and 5, they also have some missing values (represented by asterisks), assigned zero values and some null values (those that say NA, don’t know). All these issues suggest that those variables are not the key variables, and one needs to go back and double-check the data documentation. Alternatively, the archivist could check with the data producer and ask them how to fix these variables, in case those are indeed the key variables.

Table 7. Check for unique identifiers: Hypothetical data set

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Example 3 provides further details and describes the steps involved in performing a validation when the identifier is made of multiple variables (see Section A).

1.5. Identifying duplicate observations

One way to rule out problems with the unique identifier is to check if there are duplicate observations (records with identical values for all variables, not just the unique identifiers). Duplicate observations can generate erroneous analysis and cause data management problems. Some possible reasons for duplicate data are, for example, the same record being entered twice during data collection. They could also arise from an incorrect reading of the questionnaires during the scanning process if paper-based methods are being used.

Identifying duplicate observations is a crucial step. Correcting this issue may involve eliminating the duplicates from the dataset or giving them some other appropriate treatment.

Statistical packages have several commands that help identify duplicates. Table 8 shows examples of these commands in STATA, R and SPSS. The STATA command -duplicates report- generates a table that summarizes the number of copies for each record (across all variables). The command -duplicates tag- allows us to distinguish between duplicates and unique observations. For more details, refer to Example 4 of Section A.

Table 8. Check for duplicates observations: STATA/R/SPSS Commands

STATA Code R Code SPSS Function

use “household.dta”

duplicates report

duplicates tag, generate(newvar)

my_data<- load(“household.rda”)

household [duplicated(household),]

GET FILE=’household.sav’

execute.

From the menu choose:

  • Data>Indentify Duplicate Cases

1.6. Ensure that each individual dataset can be combined into a single database

For organizational purposes, surveys are often stored in different datasets. Therefore, checking the relationship between the data files is an essential step to keep in mind throughout the data validation process. The role of the data producer is to store the information as efficiently as possible, which implies storing data in different files. The role of the data user is to analyse the data as holistically as possible, which could sometimes mean that they might have to join all the different data files into a single file to facilitate analysis. It is essential to ensure that each of the separate files can be combined (merged or appended depending on the case) into a single file, should the data user want to undertake this step.

Use statistical software to validate that all files can be combined into one. For a household survey, for example, verify that all records in the individual-level files have a corresponding household in the household-level master file. Also, verify that all households have at least on e corresponding record in the household-roster file that lists all individuals. Below, some considerations to keep in mind before merging data files:

  • The variable name of the identifier should be the same across all datasets.
  • The ID variables need to be the same type (either both numeric or both string) across all databases.
  • Except for ID variables, it is highly recommended that the databases don’t share the same variable names or labels.
Example
  • A household survey is disseminated in two datasets; one contains information about household characteristics and the other contains information on the children (administered only to mothers or caretakers). To build a dataset containing all the information about the household characteristics, including where the children live, one needs to combine these files. Users are thus assured that all observations in the child-level file have corresponding household information.

Joining data files: Hypothetical data set

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Statistical packages have some commands that allows us to combine datasets using one or multiple unique identifiers. Table 9 shows examples of these commands/functions in STATA, R and SPSS. For more details, refer to Example 5 of Section A.

Table 9. Joining data files: STATA/R/SPSS Commands

STATA Code R Code SPSS Function

use “household.dta”

merge 1:m hh1 hh2 hh3 using “individuals.dta”

household<- load(“household.rda”)

individuals<- load(“individuals.rda”)

md<-merge(household, individuals, by=c(“hh1”, “hh2”, “hh3”),all=TRUE)

GET FILE=’household.sav’

execute.

From the menu choose:

  • Data>Merge Files> Add Variables
  • Select the data file to merge
  • Select Key Variables

Panel datasets should be stored in different files as well. Having one file per data collection period is a good practice. To combine the different periods of a panel dataset, the data user could merge them (Adding variables to the existing observations for the same period) or append them (Adding observations for a different period to the existing variables). To make sure that panels can be properly appended, the following checks are suggested:

  • Check for the column(s) that identifies the period of the data (Year, Wave, Serie, etc.).
  • The variable names and variable types should be the same across all datasets.
  • Ensure that the variables use the same label and the same coding across all datasets.

In SPSS, use the function “Append new records” and in STATA the command -append- to combine datasets vertically.

1.7. Check for variables with missing values

Getting data ready for documentation also involves checking for variables that do not provide complete information because they are full of missing values. This step is important because missing values can have unexpected effects on the data analysis process. Typically, missing values are defined as a character (.a, .b, single period or asterisks), special numeric (-1, -2) or blanks. Variables entirely comprised of missing values should ideally not be included in the dataset. However, before excluding them, it is useful to check whether the missing values are expected according to the questionnaire, and the skip patterns.

For example, a hypothetical household survey at the individual-level (Table 10) provides information about the respondent’s employment status. The survey identifies if the respondent is employed in Column D, and then provides information about the worker category in Column E, but only for those who reported being employed in Column D. This means that those who answered ‘unemployed’ in column D should have a valid missing value in column E. In other words, this is a pattern in the missing values that should be observed and duly noted.

On the other hand, Columns F and G are used to determine if the people who are not employed are looking for a job and are actively seeking it. These questions are not asked to the employed people (those who answered “yes” in Column D), which mean that again, the missing values in those columns correspond with what is expected. However, Column H contains information for all employed individuals, so missing values in this column suggest that there is a problem in the data and should be addressed. Therefore, one should not blindly delete missing values at the outset without checking for these patterns.

Table 10. Checking for Missing Values: Hypothetical data set

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In SPSS, use the function “Missing Value Analysis” and in R, do as shown in Table 11. You can also use the STATA command -misstable summarize- that produces a report that counts all the missing values. You can also use the -rowmiss()- command with -egen- to generate the number of missing values among the specified variables. For more details, refer to Example 6 of Section A.

Table 11. Counting Missing Values: STATA/R/SPSS Commands

STATA Code R Code SPSS Function

use “individual.dta”

misstable summarize

individual<- load(“individual.rda”)

colSums (is.na(individual))

colMeans (is.na(individual))

GET FILE= ‘individual.sav’

execute.

From the menu choose:

  • Data>Analyze> Missing Value Analysis
  • Select “Use All Variables”

Best Practices

Since there are different reasons for missing values, data producer should code them with negative integers or letters to distinguish the missing values and valid data. For instance, (− 1) might be the code for “Don’t Know”, (-2) the code for “Refused to Answer” and (-9) code for “Not Applicable”.

1.8. Check Improper value ranges

It is helpful to generate descriptive statistics for all variables (frequencies for discrete variables; min/max/mean for continuous variables) and verify that these statistics look reasonable. Just as there are variables that must take on only specific values, such as “F” and “M” for gender, there are also some variables that can take on several values (such as age or height). However, those values must fit a particular range. For example, we don’t expect negative values, or typically see values over 115 years for age.

Values for categorical variables should be guided by the questionnaire (or separate documentation for constructed variables). If we have an education variable that has 9 response options in the questionnaire, the corresponding ‘education’ variable in the dataset should have 9 categories. We should not observe more than 9 unique values for this variable. Similarly, for any questions in the survey for which the options are only “yes”, “no” and “other”, we should not observe more than these 3 unique values. When out of range values exist, this might signal data cleaning issues.

Table 12 shows examples of some commands/functions in STATA, R and SPSS.

Table 12. Generate descriptive statistics: STATA/R/SPSS Commands

STATA Code R Code SPSS Function

use “individual.dta”

summarize

individual<- load(“individual.rda”)

summary(individual)

GET FILE= ‘individual.sav’

execute.

From the menu choose:

  • Data>Analyze> Descriptive Statistics> Frequencies
  • Select “Statistics”

1.9. Verify that the number of records in each file corresponds to what is expected

The technical documentation helps to form some expectations about the size of the dataset. Make sure that in all the files, the number of records is the same as (or is similar to) what is explicitly stated in the sample design of your survey.

Suppose that you have a household survey and according to the documentation the sample size is 50,321 households. Consequently, the file that contains the household-level information should have a similar number of observations. When this is not the case, you should be able to account for this difference in data documentation.

On the other hand, even if the number of individual records is not available in the documentation, you can still perform a rough check on the files. For example, if you have the household level file and the person level file, the latter should be between 2 or 6 times larger than the former, depending on the average household size in the country for which the information has been collected. Another example is to compare the household level file of an expenditure survey with the consumption level file (at the product-level).

The latter should have n times the number of observations than the former, where n is the average number of products that each household records in the survey.

1.10. Datasets must contain all variables from the questionnaire and be in a logic sequence

Verify the completeness of your data files by comparing the content of these files with the survey questionnaire. All variables in the questionnaire should appear in the dataset, except those excluded on purpose by the producer of the data because of reasons of confidentiality (see numeral 1.15). Cross-checking with the questionnaire(s) is needed to ensure that all sections are included in the dataset.

Additionally, it is a good practice to make sure that the database is sorted in the same order as the questionnaire. This practice will help users navigate seamlessly across the dataset using the questionnaire as a route map.

The Stata command -describe- displays the names, variable labels and other characteristics, which helps us verify that no variables have been omitted in the database. It simultaneously confirms that all variables are correctly ordered. Refer to Example 7 of Section A for further details.

1.11. Include the relevant weighting coefficients and variables identifying the stratification levels

All data files of a sample survey should have clearly labelled variable(s) with information on the survey weights. Sample surveys need to be representative of a broader population for which the data is collected, and the user needs the survey weights for almost every analysis performed. In the case of household surveys, the survey weights are equal among members of the same household but differ across households. Weights are positive and strictly higher than zero. They should not have a larger value than the population for which the survey is representative.

A more detailed description of how the survey weights would look like should be provided in the documentation of the survey. Based on it, you can perform some basic range checks. Notice that Census datasets do not need weights since a census collects data on all the individuals in the population. There are however some exceptions, for example in the case of IPUMS, the data collected are not full censuses but census samples, so weights are required in this context.

Additionally, for sample surveys, verify that the variables identifying the various levels of stratification and the primary sampling unit are included and easily identifiable in at least one of the data files. These variables are needed for the calculation of sampling errors.

1.12. Variables and codes for categorical variables must be labelled

Variable labels

Labels should be short and precise. They should provide a clear indication of what information is contained in the variables. Variable labels are brief descriptions or attributes of each variable. Without variable labels, users are not able to link the variables in the database to the questions of the questionnaire. So, one should ensure that all variables are labelled.

Additionally, even if variables are fully labelled, the following practices must be considered:

  • Variable labels can be up to 80 characters long in Stata and 255 in SPSS, however, it is recommended that labels be informative, short and accurate.
  • It is a common practice to have a literal question from the survey as a variable label. However, the literal questions are usually longer than the maximum number of characters, so this is not an advisable practice.
  • The same label should not be used for two different variables.

Value labels

Label values are used for categorical variables. To ensure the correct encoding of data, it is important to check that the stored values in those variables correspond to what is expected according to the questionnaire. In the case of continuous variables, we also suggest the checking of ranges. For instance, if the question is about the number of working hours, the variable should not have negative values.

You can compare variable labels in the dataset to those in the questionnaire using the –codebook- Stata command or –labelbook-. Refer to Example 8 of Section A for further details.

1.13. Temporary, calculated or derived variables should not be disseminated

Remove all unnecessary or temporary variables from the data files. These variables are not collected in the field and present no interest for users.

The data producer could generate variables that are only needed during the quality control process but are not relevant to the final data user. For example, the variable “_merge” in Stata is generated automatically after performing the check described in the Numeral 1.6, when the data producer wants to see if the datasets match properly. Variables that group categories of a question, dummy variables that identify a question’s category are all variables produced during the coding process that are not relevant once the analysis is completed.

There are cases in which calculated variables may be useful to the users, so they must be documented in the metadata. For example, most Labor Force Surveys (LFS) contain derived dummy variables to identify the sections of the population that are employed or unemployed. These variables are generated using multiple questions from the dataset and are essential elements of any LFS. Most data users prefer to make use of them instead of computing them on their own, to reduce the risk of error. This is a strong argument to make a case for keeping these variables in the dataset, despite them being a by-product of other original variables.

To be useful, those variables that remain in the dataset must be well documented, else they, they may be useless to or misunderstood by users.

1.14. Check that the data types are correct

Do not include string variables if they can be converted into numeric variables. Look at your data and check the variables’ types, particularly for those that you expect to be numeric (age, years, number of persons/employees/hours, income, purchases/expenditures, weights, and so forth). If there are numeric variables stored as string variables, your data needs cleaning.

For example, Table 13 contains a data set at the individual-level with some variables that should be numeric. The columns B (Age) and E (Working Weeks) are stored as numeric variables, which is fine. However, the variables ‘Number of working of hours per week’ (Column G), ‘Number of persons working at the business’ (Column H) and ‘Monthly Income’ (Column I) are loaded as strings because there are non-numeric values (don’t know, skip, refused to answer) and some missing values present. Those variables need to be cleaned and converted from string variables to numeric variables.

Table 13. Checking Data Types: Hypothetical data set

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Statistical packages have some commands that allows us to make such conversions. Table 14 shows examples of these commands/functions in STATA, R and SPSS.

Table 14. Convert string variables to numeric: STATA/R/SPSS Commands

STATA Code R Code SPSS Function

use “individual.dta”

destring (varname), {generate|replace}

individual<- load(“individual.rda”)

Individual $varname = as.numeric(Individual $varname)

GET FILE= ‘individual.sav’

execute.

From the menu choose:

  • Data>Transform> Recode into Same| Different Variables
  • Select the variable
  • Select “Old and New Values” and Recode it
  • Select “Convert numeric strings to numbers (‘5’->5)

1.15. Datasets must not have directed identifiers

One must verify that in all data files, sensitive information or direct identifiers that could reveal the identity of the respondent directly (names, addresses, GPS coordinates, phone numbers, etc.) have been removed. Check to ensure this information is not in the dataset(s). If it is, those variables need to be removed from shared datasets.

Keep in mind that if you are preparing a dataset for public release, you need a cleaned, anonymous dataset. Removing all direct identifiers is the first key step to ensuring the anonymity of the participants. However, before you start any privacy procedures, you should always check your data.

For more information on how to apply statistical disclosure control (SDC) methods to data before release, see the document “Introduction to Statistical Disclosure Control (SDC)” available at http://ihsn.org/sites/default/files/resources/ihsn-working-paper-007-Oct27.pdf

1.16. Compress the variables to reduce the file size

Compress the variables consist of reducing the size of the data file without loss of precision or modifying the information that it provides. Listed below are some reasons why compressing a data set may be a useful practice for at least three reasons: First, it makes faster the process of creating backups, uploading and downloading data files from your data repository or any Survey Catalog. Second, it reduces the time that data users will need to spend working with the data. Additionally, it will make the data more accessible to the different type of users; sometimes the data size will impose restrictions on those users who lack high computational power. Third, it will help to free up disk space in the server where you store your data

Example
  • Table 15 shows two versions of one dataset that provides individual-levelinformation about the year of the first union, age, school attendance,and health insurance. There is no difference in the appearance of both datasets. However, version 1 was saving uncompressed and version 2compressed. In the uncompressed version, the variables “ID” and “Year” are stored as double, which means that they can store number with high decimal precision, but they are designed to only record information of integer numbers between -32,767 and 32,740. So, the compressed version changed the storage type of these variables to int and saves 6 bytes per observation. Similarly, other variables like “age” and “school attendance” are stored as a byte in the compressed version, which saves 7 bytes per observation when are compared to the uncompressed version. Let’s suppose that one has a data set with 500 variables like these, the total savings would be 3500 bytes per observation; if this data set has 50.000 observations, it means that the savings in memory space would be around 175 megabytes.

Table 15. Compressing the Variables: Hypothetical data set

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Use the compress command in Stata, or the compress option when you save a SPSS data file.

Suggestion:

If you are in the process of establishing a data archive and plan to document a collection of surveys, undertake a full inventory of all existing data and metadata before you start the documentation. Use the IHSN Inventory Guidelines and Forms to before you start the documentation. Use the IHSN Inventory Guidelines and Forms to facilitate this inventory (available at www.surveynetwork.org).

2. Gathering and preparing the documentation

All information related to the survey may be useful and should be archived (even if not all will be disseminated to the public). This includes not only technical documents such as the questionnaires or list of codes (obviously needed by data users), but also administrative reports (potentially useful for implementation of future surveys), and other documents such as a compilation of the comments provided by stakeholders at the time the questionnaire was designed, etc. Resources to be included if available include:

  • The survey questionnaire(s); make sure that the cover page and all sections are included. If the questionnaire exists in multiple languages, provide all versions.
  • All technical, analytical and administrative documents
    • Sampling information
    • Interviewers and supervisor’s manuals
    • List of codes
    • Instructions for data editing
    • Survey report (tabulation and analysis)
    • Analytical papers and policy briefs that made use of the data
    • Survey budget and other key planning documents
    • PowerPoint presentations and other related material
  • Computer programs (used for data entry, editing, tabulation and analysis)
  • Photos
  • Tables
  • Maps
  • Survey promotional/informational materials (flyers, videos, posters, songs, etc.)

Documents available in electronic format (MS-Word, Excel, and others) must be preserved in their original format and in PDF format.

All documents available only on hard copy must be scanned. Use low resolution graphics, and black & white option (unless it is crucial to preserve colours) to avoid large file sizes. A scanning resolution of 300 dpi is recommended. Save the scanned documents in PDF format. OCR is useful, although not required.

Scan all resources with an updated virus detection application.

3. Importing data and establishing relationships

After all data and documentation files are gathered and checked, import the data files in the Editor. In the Metadata Editor, order the files in a logical fashion (e.g., sequentially through sections).

Note

If you are documenting a population census and have very large data files, it is recommended to split the files by geographic area. Typically, you will have a file at individual level, one at the household level, and possibly one at the community level, for each State or Province. In such case, import all files for one State or Province only. You will import the other data files after you complete the documentation of the files. This will considerably reduce the time needed to save your files. The Metadata Editor will allow you to replicate the metadata from the documented files to all other data files that you will import later.

After all files are imported and ordered in a proper sequence, define the key variables for each data file. The base key variable(s) in a data file is (are) the variable(s) that provide the unique identifier of each record in that specific data file.

Then establish the relations and validate them using the Tool > Validate Dataset Relations in the Editor. This automatic validation is a way to check the structural integrity of the identifier variables and assure there are no duplicates in the data.

Establishing relationships – An example

In this example, we assume that the dataset is obtained from a household budget survey and comprises:

  • A household-level file “hhld.dat” with the household characteristics (one record per household). Each household is identified by a variable named hhid.
  • A household-level file “hhld.dat” with the household (one record per person).Each household member is identified by the combination of variables hhid and memno.
  • A consumption data file “cons.dat”, with one record per item (goods and services) per household. Each record is uniquely identified by the combination of variables hhid and itemno. The file also contains a variable district identifying the district where the household resides.
  • A data file “prices.dat” with average price per commodity, per district (one record per item per district). Each record is uniquely identified by variables district and itemno.
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In the Metadata Editor, these relationships will be established as follows in the “Key variables and relationships” section of each data file:
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If you have imported your data from any format other than fixed ASCII, re-sequence the data using the Variables > Resequence option in the Editor. This re-sequencing tool will automatically fill the “StartCol” and “EndCol” columns in the variable description section. This must be done for each data file.

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Before going further, quickly browse all variables in all data files to visually check the frequencies. This will allow you to easily spot some outliers or invalid codes, which will require recoding (which can be done in the Editor or in the source data files which will then have to be re-imported).

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Save the project. The Editor saves the full project, the associated data and documentation in one zip file. We recommend you save the project using the survey abbreviation, year and version number as project name (e.g., UGA_2018_HIES_v01_M). Note that it is good practice to avoid using spaces in a file name (use underscore characters instead).

4. Importing external resources

Before importing your external resources, create folders in the Editor as necessary (these are directories in the External Resources section in the Editor, not new directories on your hard drive). If you have very few external resources, all resources can be listed in the root directory. If you have many, organize them by type of resources (in the example below, we have created separate directories for the Questionnaires, Technical Documents, Computer Programs, Reports, Tables, Photos and Maps).
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Create an entry for each resource by entering a label in the Resource

Information field. This label should be short but explicit. Then identify the

resource file in the “Resource” field. The field “Resource” is used to indicate

the filename or URL location (website) of the external resource. The resource

consists of the filename, and a relative path. The reason for entering a relative

path is that it will allow you to move the whole study directory and its

subdirectories to another location or another drive, without having to re-enter

the location of the files.

Example:

Let’s assume your study is a Household Budget Survey conducted in 2018. If you followed the recommendations made in the introductory chapter “Before you start – Organizing your files”, you will have created a directory like C:UGA_2018_HIES. Suppose also that a document titled Report2018.pdf is saved in a directory C:UGA_2018_HIESDoc. When you fill the resource field in the External Resources page, do NOT enter “C:UGA_2018_HIESDocReport2018.pdf.pdf. Enter the file name as follows: DocReportsReport2018.pdf

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Some resources might be composed of more than one file (for example, the CSPro data entry application includes multiple files that should not be separated). In such cases, zip them into one single file, and import it as a single resource.

For documents available in multiple formats (for example, a questionnaire available in Excel and in PDF), you may create two separate resources, or zip the files into one single file. In such case, list the different formats available in the “Content/ Description” field.

Best Practices – Naming Convention for External Resources

  • Use file names short, but self-explanatory about the content of the document.
  • Preferably, use lower cases.
  • Avoid spaces to delimit words.
  • Be consistent with your method of naming across all files. For instance, if you use underscores to delimit words, keep it that way in all files.
  • Use only alphanumeric characters, underscores or dashes. Avoid using special characters (!@#$%^&*()~) or any accented characters.
  • If you intend to have an archive useable and downloadable across multiple countries, use English names for your files.

5. Completing metadata

The Metadata Editor makes use of the Data Documentation Initiative (DDI Version 2.5), the Dublin Core (DCMI version X) metadata standards and ISO 19139 for geospatial information.

The table below provides an overview of the different metadata standards as related to the project. Each metadata standard is integrated into the template that will define the project.

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A thorough completion of the DDI and DCMI elements will significantly raise the value of the archiving work by providing users with the necessary information to put the study into its proper context and to understand its purpose.

The DDI requires completion of the following sections: Document Description, Study Description, Datasets, Variables Groups, and External Resources. Recommendations for each field included in the IHSN template are provided below.

The IHSN recommends using the standardized IHSN DDI/DCMI templates (Study Template and External Resources Template). This Quick Reference Guide is based on these two templates. Visit the IHSN website to download the latest version of these templates, available in multiple languages.

Overall recommendations:

  • As an archivist, you may need to seek assistance from key experts involved in some of the technical aspects of the survey.
  • As a general rule, avoid using ALL CAPS when you fill DDI fields. Also, check the spelling of all entries. The Editor does not provide (yet) an automatic spell checker.
  • Some of the examples below present an optimal documentation of some fields. In many cases, for past surveys, you will not find such detailed information. Try to provide as much detail as possible. For future surveys, the information should be compiled and provided during the whole life cycle of the survey. This will ensure that the best possible documentation is available at completion of that survey.

5.1. Good practices for completing the Document Description

Documenting a study using the DDI and DCMI metadata standards consists of generating a metadata file which will be saved in XML format in what is called an XML Document. The Document Description described below is a description of that XML file. The IHSN Template selected 4 elements to describe the DDI document.

Metadata Producer

Name of the person(s) or organization(s) who documented the dataset. Use the “role” attribute to distinguish different stages of involvement in the production process.

Example:

Name Role
National Statistics Office (NSO) Documentation of the study
International Household Survey Network (IHSN) Review of the metadata
Date of Production This is the date (in ISO format YYYY-MM-DD) the DDI document was produced (not distributed or archived). This date will be automatically imputed when you save the file.
DDI Document Version

Documenting a dataset is not a trivial exercise. Producing “perfect” metadata is probably impossible. It may therefore happen that, having identified errors in a DDI document or having received suggestions for improvement, you decide to modify the Document even after a first version has been disseminated. This element is used to identify and describe the current version of the document. It is good practice to provide a version number (and date), and information on what distinguishes this version from the previous one(s) if relevant.

Example:
Version 02 (July 2017). This version is identical to version 01, except for the section on Data Appraisal which was updated.
DDI Document ID Number

The ID number of a DDI document is a unique number that is used to identify this DDI file. Define and use a consistent scheme to use. Such an ID could be constructed as follows: DDI_COUNTRY_PRODUCER_SURVEY_YEAR where

  • country is the 3-letter ISO country abbreviation
  • producer is the abbreviation of the producing agency
  • survey is the survey abbreviation
  • year is the reference year (or the year the survey started)
  • DDI document version number
Example:
The DDI file related to the Demographic and Health Survey documented by staff from the Uganda Bureau of Statistics in 2005 would have the following ID: DDI_UGA_UBOS_DHS_2005_v01. If the same survey is documented by a staff from the IHSN, this would be DDI_UGA_IHSN_DHS_205_v01.
Collection This field allows viewed and searched the study by collection
Programs Link surveys to projects / trust funds

5.2. Good practices for completing the Study Description

In the DDI standard, the Study Description is the section that contains all elements needed to describe the study itself (investigators, dates and methods, scope and coverage, etc.)

Identification
Survey Title

The title is the official name of the survey as it is stated on the questionnaire or as it appears in the design documents. The following items should be noted:

  • Include the reference year(s) of the survey in the title.
  • Do not include the abbreviation of the survey name in the title.
  • As the survey title is a proper noun, the first letter of each word should be capitalized (except for prepositions or other conjunctions).
  • Including the country name in the title is optional.
Example:
  • National Household Budget Survey 2012-2013
  • Popstan Multiple Indicator Cluster Survey 2012
Survey Subtitle

Subtitle is optional and rarely used. A subtitle can be used to add information usually associated with a sequential qualifier for a survey.

Example:

Title: Welfare Monitoring Survey 2007

Subtitle: Fifth round

Abbreviation or Acronym

The abbreviation of a survey is usually the first letter of each word of the titled survey. The survey reference year(s) may be included.

Example:
  • DHS 2015 for “Demographic and Health Survey 2005”
  • HIES 2012-2013 for “Household Income and Expenditure Survey 2003”
Study type The study type or survey type is the broad category defining the survey. This item has a controlled vocabulary (you may customize the IHSN template to adjust this controlled vocabulary if needed).
Series information

A survey may be repeated at regular intervals (such as an annual labour force survey), or be part of an international survey program (such as the MICS, CWIQ, DHS, LSMS and others). The Series information is a description of this “collection” of surveys. A brief description of the characteristics of the survey, including when it started, how many rounds were already implemented, and who is in charge would be provided here. If the survey does not belong to a series, leave this field empty.

Example:

The Multiple Indicator Cluster Survey, Round 3 (MICS3) is the third round of MICS surveys, previously conducted around 1995 (MICS1) and 2000 (MICS2). MICS surveys are designed by UNICEF, and implemented by national agencies in participating countries. MICS was designed to monitor various indicators identified at the World Summit for Children and the Millennium Development Goals. Many questions and indicators in MICS3 are consistent and compatible with the prior round of MICS (MICS2) but less so with MICS1, although there have been a number of changes in definition of indicators between rounds.

Round 1 covered X countries, round 2 covered Y countries, and Round Z covered N countries.

Translated title In countries with more than one official language, a translation of the title may be provided. Likewise, the translated title may simply be a translation into English from a country’s own language. Special characters should be properly displayed (such as accents and other stress marks or different alphabets).
Unique user defined ID Number

The ID number of a dataset is a unique number that is used to identify a particular survey. Define and use a consistent scheme to use. Such an ID could be constructed as follows: country-producer-survey-year-vers ion where

  • country is the 3-letter ISO country abbreviation
  • producer is the abbreviation of the producing agency
  • survey is the survey abbreviation
  • year is the reference year (or the year the survey started)
  • version is the number dataset version number (see Version Description below)
Example:

The Demographic and Health Survey implemented by the Uganda Bureau of Statistics in 2005 could have the following ID:

UGA-UBOS-DHS-2005-v01.

Depositor The name of the person (or institution) who provided this data collection to the archive storing it.
Date of Deposit The date that the data collection was deposited with the archive that originally received it.
Version
Version Description

The version description should contain a version number followed by a version label. The version number should follow a standard convention to be adopted by the institute. We recommend that larger series be defined by a number to the left of a decimal and iterations of the same series by a sequential number that identifies the release. Larger series will typically include (0) the raw, unedited dataset; (1) the edited dataset, non anonymized, for internal use at the data producing agency; and (2) the edited dataset, prepared for dissemination to secondary users (possibly anonymized).

Example:
  • v00: Basic raw data, obtained from data entry (before editing).
  • v01: Edited data, second version, for internal use only.
  • v02: Edited, anonymous dataset for public distribution.

A brief description of the version should follow the numerical identification.

Production date This is the date in ISO format (yyyy-mm-dd) of actual and final production of the data. Production dates of all versions should be carefully tracked. Provide at least the month and year. Use the calendar icon in the Metadata editor to assure that the date selected is in compliance with the ISO format.
Version Notes Version notes should provide a brief report on the changes made through the versioning process. The note should indicate how this version differs from other versions of the same dataset.
Study Authorization
Authorizing Agency Name of the agent or agency that authorized the study. The “affiliation” attribute indicates the institutional affiliation of the authorizing agent or agency. The “abbr” attribute holds the abbreviation of the authorizing agent’s or agency’s name
Authorization Statement

The text of the authorization. Use XHTML to capture significant structure in the document

Example:

Required documentation covering the study purpose, disclosure information, questionnaire content, and consent statements was delivered to the OUHS on 2010-10-01 and reviewed by the compliance officer. Statement of authorization for the described study was received on 2010-11-04

Legal basis Decree or law authorizing or requiring the study (e.g. census act)
Overview
Study Budget

Describe the budget of the project in as much detail as needed. Internal structure is allowed using XHTML elements. Different organizations express their budgets in different formats and this open format allows flexibility.

Attributes: Budget line ID, Budget line label, Amount, Currency and Source of funding.

Abstract The abstract should provide a clear summary of the purposes, objectives and content of the survey. It should be written by a researcher or survey statistician aware of the survey.
Objectives of the study Describe the Main (explicit) and secondary (explicit) objectives of the survey.
Kind of data This field is a broad classification of the data and it is associated with a drop-down box providing controlled vocabulary. That controlled vocabulary includes 9 items but is not limited to them.
Unit of analysis

A survey could have various units of analysis. These are fairly standard and are usually:

  • Household (household survey, census)
  • Person (household survey, census)
  • Enterprise (enterprise survey)
  • Commodity (household survey, price survey)
  • Plots of land (agricultural survey)
Scope
Description of scope

The scope is a description of the themes covered by the survey. It can be viewed as a summary of the modules that are included in the questionnaire. The scope does not deal with geographic coverage.

Example:

The scope of the Multiple Indicator Cluster Survey includes:

  • HOUSEHOLD: Household characteristics, household listing, orphaned and vulnerable children, education, child labour, water and sanitation, household use of insecticide treated mosquito nets, and salt iodization, with optional modules for child discipline, child disability, maternal mortality and security of tenure and durability of housing.
  • WOMEN: Women’s characteristics, child mortality, tetanus toxoid, maternal and newborn health, marriage, polygyny, female genital cutting, contraception, and HIV/AIDS knowledge, with optional modules for unmet need, domestic violence, and sexual behavior.
  • CHILDREN: Children’s characteristics, birth registration and early learning, vitamin A, breastfeeding, care of illness, malaria, immunization, and anthropometry, with an optional module for child development.
Topic classifications A topic classification facilitates referencing and searches in electronic survey catalogs. Topics should be selected from a standard thesaurus, preferably an international, multilingual thesaurus. The IHSN recommends the use of the thesaurus used by the Council of European Social Science Data Archives (CESSDA). The CESSDA thesaurus has been introduced as a controlled vocabulary in the IHSN Study Template version 1.3 (available www.surveynetwork.org/toolkit).
Keywords Keywords summarize the content or subject matter of the survey. As topic classifications, these are used to facilitate referencing and searches in electronic survey catalogs. Keywords should be selected from a standard thesaurus, preferably an international, multilingual thesaurus. Entering a list of keywords is tedious. This option is provided for advanced users only.
Quality Statement
Standards Compliance This section lists all specific standards complied with during the execution of this study. Note the standard name and producer and how the study complied with the standard
Other Quality Statement Enter any additional quality statements
Post Evaluation Procedures
Evaluator Type

The evaluator element identifies persons or organizations involved in the evaluation. The Affiliation attribute contains the affiliation of the individual or organization. The Abbr. attribute holds an abbreviation for the individual or organization. The Role attribute indicates the role played by the individual or organization in the evaluation process.

Example:

  • Affiliation: United Nations
  • Abbr.: UNSD
  • Role: Consultant
Evaluation Process Describes the evaluation process followed. Ex-Post Evaluations are frequently done within large statistical or research agencies, in particular when the survey is intended to be repeated or on-going
Evaluation Outcomes Describe the outcomes of the evaluation
Coverage
Country Enter the country name, even in cases where the survey did not cover the entire country. In the field “Abbreviation”, we recommend that you enter the 3-letter ISO code of the country. If the dataset you document covers more than one country, enter all in separate rows.
Geographic coverage

This filed aims at describing at what geographic level the data are representative. Typical entries will be “National coverage”, “Urban (or rural) areas only”, “state of …”, “Capital city”, etc.

Note that we do not describe here where the data was collected. For example, as sample survey could be declared as “national coverage” even in cases where some districts where not included in the sample, as long as the sampling strategy was such that the representativity is national.

Geographic Unit Lowest level of geographic aggregation covered by the data.
Universe

We are interested here in the survey universe (not the universe of particular sections of the questionnaires or variables), i.e. in the identification of the population of interest in the survey. The universe will rarely be the entire population of the country. Sample household surveys, for example, usually do not cover homeless, nomads, diplomats, community households. Population censuses do not cover diplomats. Try to provide the most detailed information possible on the population covered by the survey/census.

Example:
The survey covered all de jure household members (usual residents), all women aged 15-49 years resident in the household, and all children aged 0-4 years (under age 5) resident in the household.
Geographic bounding box The geographic bounding box is the minimum box, defined by west and east longitudes and north and south latitudes, that includes the largest geographic extent of the dataset’s geographic coverage. This element is used in the first pass of a coordinate-based search. If the Geographic bounding Polygon element is included, then this field element MUST be included
Geographic Bounding Polygon

This field allows the creation of multiple polygons to describe in a more detailed manner the geographic area covered by the dataset. It should only be used to define the outer boundaries of a covered area.

Example: In the United States, such polygons can be created to define boundaries for Hawaii, Alaska, and the continental United States, but not interior boundaries for the contiguous states. This field is used to refine a coordinate-based search, not to actually map an area

Producers and Sponsors.
Authoring Entity/Primary investigators The primary investigator will in most cases be an institution, but could also be an individual in the case of small-scale academic surveys. The two fields to be completed are the Name and the Affiliation fields. Generally, in a survey, the Primary Investigator will be the institution implementing the survey. If various institutions have been equally involved as main investigators, then all should be mentioned. This only includes the agencies responsible for the implementation of the survey, not its funding or technical assistance. The order in which they are listed is discretionary. It can be alphabetic or by significance of contribution. Individual persons can also be mentioned. If persons are mentioned use the appropriate format of Surname, First name.
Producers

This field is provided to list other interested parties and persons that have played a significant but not the leading technical role in implementing and producing the data. The specific fields to be competed are: Name of the organization, Abbreviation, Affiliation and Role. If any of the fields are not applicable these can be left blank. The abbreviations should be the official abbreviation of the organization. The role should be a short and succinct phrase or description on the specific assistance provided by the organization in order to produce the data. The roles should be standard vocabulary such as:

  • [Technical assistance in] questionnaire design
  • [Technical assistance in] sampling methodology / selection
  • [Technical assistance in] data collection
  • [Technical assistance in] data processing
  • [Technical assistance in] data analysis

Do not include here the financial sponsors.

Funding Agency/Sponsor List the organizations (national or international) that have contributed, in cash or in kind, to the financing of the survey. The government institution that has provided funding should not be forgotten.
Other Identifications/ acknowledgements This optional field can be used to acknowledge any other people and institutions that have in some form contributed to the survey.
Sampling
Sampling procedure

This field only applies to sample surveys. Information on sampling procedure is crucial (although not applicable for censuses and administrative datasets). This section should include summary information that includes though is not limited to:

  • Sample size
  • Selection process (e.g., probability proportional to size or over sampling)
  • Stratification (implicit and explicit)
  • Stages of sample selection
  • Design omissions in the sample
  • Level of representation
  • Strategy for absent respondents/not found/refusals (replacement or not)
  • Sample frame used, and listing exercise conducted to update it

It is useful also to indicate here what variables in the data files identify the various levels of stratification and the primary sample unit. These are crucial to the data users who want to properly account for the sampling design in their analyses and calculations of sampling errors.

This section accepts only text format; formulae cannot be entered. In most cases, technical documents will exist that describe the sampling strategy in detail. In such cases, include here a reference (title/author/date) to this document, and make sure that the document is provided in the External Resources.

Example:
5000 households were selected for the sample. Of these, 4996 were occupied households and 4811 were successfully interviewed for a response rate of 96.3%. Within these households, 7815 eligible women aged 15-49 were identified for interview, of which 7505 were successfully interviewed (response rate 96.0%), and 3242 children aged 0-4 were identified for whom the mother or caretaker was successfully interviewed for 3167 children (response rate 97.7%). These give overall response rates (household response rate times individual response rate) for the women’s interview of 92.5% and for the children’s interview of 94.1%.
Sample Frame Name Sample frame describes the sampling frame used for identifying the population from which the sample was taken. Label and text describing the sample frame
Update of listing Describes operations conducted to update the sample frame
Valid Period Defines a time period for the validity of the sampling frame. Enter dates in YYYY-MM-DD format.
Custodian Custodian identifies the agency or individual who is responsible for creating or maintaining the sample frame. Attribute affiliation provides the affiliation of the custodian with an agency or organization. Attribute abbr. provides an abbreviation for the custodian.
Use Statement Sample frame use statement
Frame Unit Provides information about the sampling frame unit. The attribute “is Primary” is boolean, indicating whether the unit is primary or not.
Reference Period Indicates the period of time in which the sampling frame was actually used for the study in question. Use ISO 8601 date/time formats to enter the relevant date(s).
Sample Size

This element provides the targeted sample size in integer format.

Attributes: Planned / Actual and Unit and Number.

Sample Size Formula This element includes the formula that was used to determine the sample size
Stratification Describe the Stratification (implicit and explicit) and the Variables identifying strata and PSU
Deviation from sample design

This field only applies to sample surveys.

Sometimes the reality of the field requires a deviation from the sampling design (for example due to difficulty to access to zones due to weather problems, political instability, etc). If for any reason, the sample design has deviated, this should be reported here.

Response rate

Response rate provides that percentage of households (or other sample unit) that participated in the survey based on the original sample size. Omissions may occur due to refusal to participate, impossibility to locate the respondent, or other. Sometimes, a household may be replaced by another by design. Check that the information provided here is consistent with the sample size indicated in the “Sampling procedure field” and the number of records found in the dataset (for example, if the sample design mention a sample of 5,000 households and the data on contain data on 4,500 households, the response rate should not be 100 percent).

Provide if possible the response rates by stratum. If information is available on the causes of non-response (refusal/not found/other), provide this information as well.

This field can also in some cases be used to describe non-responses in population censuses.

Weighting

This field only applies to sample surveys.

Provide here the list of variables used as weighting coefficient. If more than one variable is a weighting variable, describe how these variables differ from each other and what the purpose of each one of them is.

Example:

Sample weights were calculated for each of the data files.

Sample weights for the household data were computed as the inverse of the probability of selection of the household, computed at the sampling domain level (urban/rural within each region). The household weights were adjusted for non-response at the domain level, and were then normalized by a constant factor so that the total weighted number of households equals the total unweighted number of households. The household weight variable is called HHWEIGHT and is used with the HH data and the HL data.

Sample weights for the women’s data used the un-normalized household weights, adjusted for non-response for the women’s questionnaire, and were then normalized by a constant factor so that the total weighted number of women’s cases equals the total unweighted number of women’s cases.

Sample weights for the children’s data followed the same approach as the women’s and used the un-normalized household weights, adjusted for non-response for the children’s questionnaire, and were then normalized by a constant factor so that the total weighted number of children’s cases equals the total unweighted number of children’s cases.

Data Collection
Dates of data collection

Enter the dates (at least month and year) of the start and end of the data collection. They should be in the standard ISO format of YYYY-MM-DD.

In some cases, data collection for a same survey can be conducted in waves. In such case, you should enter the start and end date of each wave separately, and identify each wave in the “cycle” field.

Collector Training Describes the training provided to data collectors including interviewer training, process testing, compliance with standards etc. This is repeatable for language and to capture different aspects of the training process. The type attribute allows specification of the type of training being described
Frequency of Data Collection For data collected at more than one point in time, the frequency with which the data were collected. The “freq” attribute is included to permit the development of a controlled vocabulary for this element.
Time period This field will usually be left empty. Time period differs from the dates of collection as they represent the period for which the data collected are applicable or relevant.
Data Sources Used to list the book(s), article(s), serial(s), and/or machine-readable data file(s)–if any–that served as the source(s) of the data collection
Alternatives to data collection Sources of data available / potentially considered
Mode of data collection The mode of data collection is the manner in which the interview was conducted or information was gathered. This field is a controlled vocabulary field. Use the drop-down button in the Toolkit to select one option. In most cases, the response will be “face to face interview”. But for some specific kinds of datasets, such as for example data on rain falls, the response will be different.
Data Capture Where was data capture done (e.g., In the field or at the office) and when was data capture done. Also, describe the technology using for data capture (e.g. scanning, PDAs OR Web)
Notes on data collection

This element is provided in order to document any specific observations, occurrences or events during data collection. Consider stating such items like:

  • Was a training of enumerators held? (elaborate)
  • Any events that could have a bearing on the data quality?
  • How long did an interview take on average?
  • Was there a process of negotiation between households, the community and the implementing agency?
  • Are anecdotal events recorded?
  • Have the field teams contributed by supplying information on issues and occurrences during data collection?
  • In what language was the interview conducted?
  • Was a pilot survey conducted?
  • Were there any corrective actions taken by management when problems occurred in the field?
Example:

The pre-test for the survey took place from August 15, 2006 - August 25, 2006 and included 14 interviewers who would later become supervisors for the main survey.

Each interviewing team comprised of 3-4 female interviewers (no male interviewers were used due to the sensitivity of the subject matter), together with a field editor and a supervisor and a driver. A total of 52 interviewers, 14 supervisors and 14 field editors were used. Data collection took place over a period of about 6 weeks from September 2, 2006 until October 17, 2006. Interviewing took place everyday throughout the fieldwork period, although interviewing teams were permitted to take one day off per week.

Interviews averaged 35 minutes for the household questionnaire (excluding salt testing), 23 minutes for the women’s questionnaire, and 27 for the under five children’s questionnaire (excluding the anthropometry). Interviews were conducted primarily in English and Mumbo-jumbo, but occasionally used local translation in double-Dutch, when the respondent did not speak English or Mumbo-jumbo.

Six staff members of GenCenStat provided overall fieldwork coordination and supervision. The overall field coordinator was Mrs. Doe.

Questionnaires

This element is provided to describe the questionnaire(s) used for the data collection. The following should be mentioned:

  • List of questionnaires and short description of each (all questionnaires must be provided as External Resources)
  • In what language were the questionnaires published?
  • Information on the questionnaire design process (based on a previous questionnaire, based on a standard model questionnaire, review by stakeholders). If a document was compiled that contains the comments provided by the stakeholders on the draft questionnaire, or a report prepared on the questionnaire testing, a reference to these documents should be provided here and the documents should be provided as External Resources.
Example:

The questionnaires for the Generic MICS were structured questionnaires based on the MICS3 Model Questionnaire with some modifications and additions. A household questionnaire was administered in each household, which collected various information on household members including sex, age, relationship, and orphanhood status. The household questionnaire includes household characteristics, support to orphaned and vulnerable children, education, child labour, water and sanitation, household use of insecticide treated mosquito nets, and salt iodization, with optional modules for child discipline, child disability, maternal mortality and security of tenure and durability of housing.

In addition to a household questionnaire, questionnaires were administered in each household for women age 15-49 and children under age five. For children, the questionnaire was administered to the mother or caretaker of the child.

The women’s questionnaire include women’s characteristics, child mortality, tetanus toxoid, maternal and newborn health, marriage, polygyny, female genital cutting, contraception, and HIV/AIDS knowledge, with optional modules for unmet need, domestic violence, and sexual behavior.

The children’s questionnaire includes children’s characteristics, birth registration and early learning, vitamin A, breastfeeding, care of illness, malaria, immunization, and anthropometry, with an optional module for child development.

The questionnaires were developed in English from the MICS3 Model Questionnaires, and were translated into Mumbo-jumbo. After an initial review the questionnaires were translated back into English by an independent translator with no prior knowledge of the survey. The back translation from the Mumbo-jumbo version was independently reviewed and compared to the English original. Differences in translation were reviewed and resolved in collaboration with the original translators.

The English and Mumbo-jumbo questionnaires were both piloted as part of the survey pretest.

All questionnaires and modules are provided as external resources.

Instrument Development Describe any development work on the data collection instrument. Type attribute allows for the optional use of a defined development type with or without use of a controlled vocabulary.
Review process for survey instrument Description of the review process / list of agencies/people consulted
Pilot/testing of survey instrument and data collection Description of pilot survey
Survey management team Attributes: Name, Tittle, Agency, Role
Data collectors

This element is provided in order to record information regarding the persons and/or agencies that took charge of the data collection. This element includes 3 fields: Name, Abbreviation, the Affiliation and the Role. In most cases, we will record here the name of the agency, not the name of interviewers. Only in the case of very small-scale surveys, with a very limited number of interviewers, the name of person will be included as well. The field Affiliation is optional and not relevant in all cases. The role attribute specifies the role of person in the data collection process.

Example:

Abbreviation: CSO

Affiliation: Ministry of Planning

Role: Planner

Compliance with international data collection standards Describe if the survey comply with international survey recommendations
Supervision

This element will provide information on the oversight of the data collection. The following should be considered:

  • Were the enumerators organized in teams that included a controller and a supervisor? With how many controllers/supervisors per interviewer?
  • What were the main roles of the controllers/supervisors?
  • Were there visits to the field by upper management? How often?
Example:

Interviewing was conducted by teams of interviewers. Each interviewing team comprised of 3-4 female interviewers, a field editor and a supervisor, and a driver. Each team used a 4 wheel drive vehicle to travel from cluster to cluster (and where necessary within cluster).

The role of the supervisor was to coordinator field data collection activities, including management of the field teams, supplies and equipment, finances, maps and listings, coordinate with local authorities concerning the survey plan and make arrangements for accommodation and travel. Additionally, the field supervisor assigned the work to the interviewers, spot checked work, maintained field control documents, and sent completed questionnaires and progress reports to the central office.

The field editor was responsible for reviewing each questionnaire at the end of the day, checking for missed questions, skip errors, fields incorrectly completed, and checking for inconsistencies in the data. The field editor also observed interviews and conducted review sessions with interviewers.

Responsibilities of the supervisors and field editors are described in the Instructions for Supervisors and Field Editors, together with the different field controls that were in place to control the quality of the fieldwork.

Field visits were also made by a team of central staff on a periodic basis during fieldwork. The senior staff of GenCenStat also made 3 visits to field teams to provide support and to review progress.

Data Processing  
Data entry and editing

The data editing should contain information on how the data was treated or controlled for in terms of consistency and coherence. This item does not concern the data entry phase but only the editing of data whether manual or automatic.

  • Was a hot deck or a cold deck technique used to edit the data?
  • Were corrections made automatically (by program), or by visual control of the questionnaire?
  • What software was used?

If materials are available (specifications for data editing, report on data editing, programs used for data editing), they should be listed here and provided as external resources.

Example:

Data editing took place at a number of stages throughout the processing, including:

a) Office editing and coding

b) During data entry

c) Structure checking and completenes

d) Secondary editing

e) Structural checking of SPSS data files

Detailed documentation of the editing of data can be found in the “Data processing guidelines” document provided as an external resource.

Software

List of software used for the key activities (especially data entry, editing, tabulation, analysis).

Attributes: Purpose and Software

Other processing

Use this field to provide as much information as possible on the data entry design. This includes such details as:

  • Mode of data entry (manual or by scanning, in the field/in regions/at headquarters)
  • Computer architecture (laptop computers in the field, desktop computers, scanners, PDA, other; indicate the number of computers used)
  • Software used
  • Use (and rate) of double data entry
  • Average productivity of data entry operators; number of data entry operators involved and their work schedule

Information on tabulation and analysis can also be provided here.

All available materials (data entry/tabulation/analysis programs; reports on data entry) should be listed here and provided as external resources.

Example:
Data were processed in clusters, with each cluster being processed as a complete unit through each stage of data processing. Each cluster goes through the following steps:
  1. Questionnaire reception
  2. Office editing and coding
  3. Data entry
  4. Structure and completeness checking
  5. Verification entry
  6. Comparison of verification data
  7. Back up of raw data
  8. Secondary editing
  9. Edited data back up

After all clusters are processed, all data is concatenated together and then the following steps are completed for all data files:

  1. Export to SPSS in 4 files (hh - household, hl - household members, wm - women, ch - children under 5)
  2. Recoding of variables needed for analysis
  3. Adding of sample weights
  4. Calculation of wealth quintiles and merging into data
  5. Structural checking of SPSS files
  6. Data quality tabulations
  7. Production of analysis tabulations

Details of each of these steps can be found in the data processing documentation, data editing guidelines, data processing programs in CSPro and SPSS, and tabulation guidelines.

Data entry was conducted by 12 data entry operators in tow shifts, supervised by 2 data entry supervisors, using a total of 7 computers (6 data entry computers plus one supervisors’ computer). All data entry was conducted at the GenCenStat head office using manual data entry. For data entry, CSPro version 2.6.007 was used with a highly structured data entry program, using system controlled approach that controlled entry of each variable. All range checks and skips were controlled by the program and operators could not override these. A limited set of consistency checks were also included in the data entry program. In addition, the calculation of anthropometric Z-scores was also included in the data entry programs for use during analysis. Open-ended responses (“Other” answers) were not entered or coded, except in rare circumstances where the response matched an existing code in the questionnaire.

Structure and completeness checking ensured that all questionnaires for the cluster had been entered, were structurally sound, and that women’s and children’s questionnaires existed for each eligible woman and child.

100% verification of all variables was performed using independent verification, i.e. double entry of data, with separate comparison of data followed by modification of one or both datasets to correct keying errors by original operators who first keyed the files.

After completion of all processing in CSPro, all individual cluster files were backed up before concatenating data together using the CSPro file concatenate utility.

For tabulation and analysis SPSS versions 10.0 and 14.0 were used. Version 10.0 was originally used for all tabulation programs, except for child mortality. Later version 14.0 was used for child mortality, data quality tabulations and other analysis activities.

After transferring all files to SPSS, certain variables were recoded for use as background characteristics in the tabulation of the data, including grouping age, education, geographic areas as needed for analysis. In the process of recoding ages and dates some random imputation of dates (within calculated constraints) was performed to handle missing or “don’t know” ages or dates. Additionally, a wealth (asset) index of household members was calculated using principal components analysis, based on household assets, and both the score and quintiles were included in the datasets for use in tabulations.

Coding Instructions
Coding Instructions Text

Describe specific coding instructions used in data processing, cleaning, assession, or tabulation. Use this field to describe instructions in a human readable form.

Example:
Due to an error in the data collection system the value of “27” was entered for the variable NBWFBPC which should be coded as an invalid value of “99”
Command

Provide command code for the coding instruction. The formalLanguage attribute identifies the language of the command code.

Example:
SPSS”>RECODE V1 TO V100 (10 THROUGH HIGH = 0)
Data Appraisal
Estimate of sampling error

For sampling surveys, it is good practice to calculate and publish sampling error. This field is used to provide information on these calculations. This includes:

  • A list of ratios/indicators for which sampling errors were computed.
  • Details regarding the software used for computing the sampling error, and reference to the programs used (to be provided as external resources) as the program used to perform the calculations.
  • Reference to the reports or other document where the results can be found (to be provided as external resources).
Example:

Estimates from a sample survey are affected by two types of errors: 1) non-sampling errors and 2) sampling errors. Non-sampling errors are the results of mistakes made in the implementation of data collection and data processing. Numerous efforts were made during implementation of the 2005-2006 MICS to minimize this type of error, however, non-sampling errors are impossible to avoid and difficult to evaluate statistically.

If the sample of respondents had been a simple random sample, it would have been possible to use straightforward formulae for calculating sampling errors. However, the 2005-2006 MICS sample is the result of a multi-stage stratified design, and consequently needs to use more complex formulae. The SPSS complex samples module has been used to calculate sampling errors for the 2005-2006 MICS. This module uses the Taylor linearization method of variance estimation for survey estimates that are means or proportions. This method is documented in the SPSS file CSDescriptives.pdf found under the Help, Algorithms options in SPSS.

Sampling errors have been calculated for a select set of statistics (all of which are proportions due to the limitations of the Taylor linearization method) for the national sample, urban and rural areas, and for each of the five regions. For each statistic, the estimate, its standard error, the coefficient of variation (or relative error – the ratio between the standard error and the estimate), the design effect, and the square root design effect (DEFT – the ratio between the standard error using the given sample design and the standard error that would result if a simple random sample had been used), as well as the 95 percent confidence intervals (+/-2 standard errors).

Details of the sampling errors are presented in the sampling errors appendix to the report and in the sampling errors table presented in the external resources.

Other forms data appraisal

This section can be used to report any other action taken to assess the reliability of the data, or any observations regarding data quality. This item can include:

  • For a population census, information on the post enumeration survey (a report should be provided in external resources and mentioned here).
  • For any survey/census, a comparison with data from another source.
  • Etc.
Example:
A series of data quality tables and graphs are available to review the quality of the data and include the following:
  • Age distribution of the household population
  • Age distribution of eligible women and interviewed women
  • Age distribution of eligible children and children for whom the mother or caretaker was interviewed
  • Age distribution of children under age 5 by 3 month groups
  • Age and period ratios at boundaries of eligibility
  • Percent of observations with missing information on selected variables
  • Presence of mother in the household and person interviewed for the under 5 questionnaire
  • School attendance by single year age
  • Sex ratio at birth among children ever born, surviving and dead by age of respondent
  • Distribution of women by time since last birth
  • Scatter plot of weight by height, weight by age and height by age
  • Graph of male and female population by single years of age
  • Population pyramid

The results of each of these data quality tables are shown in the appendix of the final report and are also given in the external resources section.

The general rule for presentation of missing data in the final report tabulations is that a column is presented for missing data if the percentage of cases with missing data is 1% or more. Cases with missing data on the background characteristics (e.g. education) are included in the tables, but the missing data rows are suppressed and noted at the bottom of the tables in the report (not in the SPSS output, however).

Data Access
Access authority This section is composed of various sections: Name-Affiliation-email-URI. This information provides the contact person or entity to gain authority to access the data. It is advisable to use a generic email contact such as data@popstatsoffice.org whenever possible to avoid tying access to a particular individual whose functions may change over time.
Confidentiality Declaration

If the dataset is not anonymized, we may indicate here what Affidavit of Confidentiality must be signed before the data can be accessed. Another option is to include this information in the next element (Access conditions). If there is no confidentiality issue, this field can be left blank.

An example of statement could be the following:

Confidentiality of respondents is guaranteed by Articles N to NN of the National Statistics Act of [date].

Before being granted access to the dataset, all users have to formally agree:

  1. To make no copies of any files or portions of files to which s/he is granted access except those authorized by the data depositor.
  2. Not to use any technique in an attempt to learn the identity of any person, establishment, or sampling unit not identified on public use data files.
  3. To hold in strictest confidence the identification of any establishment or individual that may be inadvertently revealed in any documents or discussion, or analysis. Such inadvertent identification revealed in her/his analysis will be immediately brought to the attention of the data depositor.

This statement does not replace a more comprehensive data agreement(see Access condition).

Access conditions

Each dataset should have an “Access policy” attached to it. The IHSN recommends three levels of accessibility:

  • Public use files, accessible to all
  • Licensed datasets, accessible under conditions
  • Datasets only accessible in a data enclave, for the most sensitive and confidential data.

The IHSN has formulated standard, generic policies and access forms for each one of these three levels (which each country can customize to its specific needs). One of the three policies may be copy/pasted in this field once it has been edited as needed and approved by the appropriate authority. Before you fill this field, a decision has to be made by the management of the data depositor agency. Avoid writing a specific statement for each dataset.

If the access policy is subject to regular changes, you should enter here a URL where the user will find detailed information on access policy which applies to this specific dataset. If the datasets are sold, pricing information should also be provided on a website instead of being entered here.

If the access policy is not subject to regular changes, you may enter more detailed information here. For a public use file for example, you could enter information like:

The dataset has been anonymized and is available as a Public Use Dataset. It is accessible to all for statistical and research purposes only, under the following terms and conditions:

  1. The data and other materials will not be redistributed or sold to other individuals, institutions, or organizations without the written agreement of the [National Data Archive].
  2. The data will be used for statistical and scientific research purposes only. They will be used solely for reporting of aggregated information, and not for investigation of specific individuals or organizations.
  3. No attempt will be made to re-identify respondents, and no use will be made of the identity of any person or establishment discovered inadvertently. Any such discovery would immediately be reported to the [National Data Archive].
  4. No attempt will be made to produce links among datasets provided by the [National Data Archive], or among data from the [National Data Archive] and other datasets that could identify individuals or organizations.
  5. Any books, articles, conference papers, theses, dissertations, reports, or other publications that employ data obtained from the [National Data Archive] will cite the source of data in accordance with the Citation Requirement provided with each dataset.
  6. An electronic copy of all reports and publications based on the requested data will be sent to the [National Data Archive].
  7. The original collector of the data, the [National Data Archive], and the relevant funding agencies bear no responsibility for use of the data or for interpretations or inferences based upon such uses.
Citation requirement

Citation requirement is the way that the dataset should be referenced when cited in any publication. Every dataset should have a citation requirement. This will guarantee that the data producer gets proper credit, and that analytical results can be linked to the proper version of the dataset. The Access Policy should explicitly mention the obligation to comply with the citation requirement (in the example above, see item 5). The citation should include at least the primary investigator, the name and abbreviation of the dataset, the reference year, and the version number. Include also a website where the data or information on the data is made available by the official data depositor.

Example:
“National Statistics Office of Popstan, Multiple Indicators Cluster Survey 2000 (MICS 2000), Version 01 of the public use dataset (April 2001), provided by the National Data Archive. www.nda_popstan.org”
Location of Data Collection Location where the data collection is currently stored. Use the URI attribute to provide a URN or URL for the storage site or the actual address from which the data may be downloaded.
URL for Location of Data Collection Location where the data collection is currently stored. Provide a URN or URL for the storage site or the actual address from which the data may be downloaded.
Archive Where Study Originally Stored Statement of collection availability. An archive may need to indicate that a collection is unavailable because it is embargoed for a period of time, because it has been superseded, because a new edition is imminent, etc. It is anticipated that a controlled vocabulary will be developed for this element.
Availability Status Statement of collection availability. An archive may need to indicate that a collection is unavailable because it is embargoed for a period of time, because it has been superseded, because a new edition is imminent, etc. It is anticipated that a controlled vocabulary will be developed for this element.
Deposit Requirement Information regarding user responsibility for informing archives of their use of data through providing citations to the published work or providing copies of the manuscripts.
Disclaimer and Copyright
Disclaimer

A disclaimer limits the liability that the Statistics Office has regarding the use of the data. A standard legal statement should be used for all datasets from a same agency. The IHSN recommends the following formulation:

The user of the data acknowledges that the original collector of the data, the authorized distributor of the data, and the relevant funding agency bear no responsibility for use of the data or for interpretations or inferences based upon such uses.

Copyright

Include here a copyright statement on the dataset, such as:

© 2017, Popstan Central Statistics Agency

Contacts
Contact persons

Users of the data may need further clarification and information. This section may include the name-affiliation-email-URI of one or multiple contact persons. Avoid putting the name of individuals. The information provided here should be valid for the long term. It is therefore preferable to identify contact persons by a title. The same applies for the email field. Ideally, a “generic” email address should be provided. It is easy to configure a mail server in such a way that all messages sent to the generic email address would be automatically forwarded to some staff members.

Example:

Name: Head, Data Processing Division

Affiliation: National Statistics Office

Email: dataproc@cso.org

URI: www.cso.org/databank

5.3. Good practices for completing the File Description

The File Description is the DDI section that aims to provide a detailed description of each data file. The IHSN has selected six of the available DDI elements.

File Citation Provides for a full bibliographic citation option for each data file described in File Description.
Contents of Files

A data filename usually provides little information on its content. Provide here a description of this content. This description should clearly distinguish collected variables and derived variables. It is also useful to indicate the availability in the data file of some particular variables such as the weighting coefficients. If the file contains derived variables, it is good practice to refer to the computer program that generated it.

Examples:
  • The file contains data related to section 3A of the household survey questionnaire (Education of household members aged 6 to 24 years). It also contains the weighting coefficient, and various recoded variables on levels of education.
  • The file contains derived data on household consumption, annualized and aggregated by category of products and services. The file also contains a regional price deflator variable and the household weighting coefficient. The file was generated using a Stata program named “cons_aggregate.do” available in the external resources.
File Producer Put the name of the agency that produced the data file. Most data files will have been produced by the survey primary investigator. In some cases however, auxiliary or derived files from other producers may be released with a data set. This may for example include CPI data generated by a different agency, or files containing derived variables generated by a researcher.
Version A data file may undergo various changes and modifications. These file specific versions can be tracked in this element. This field will in most cases be left empty. It is more important to fill the field identifying the version of the dataset (see above).
Processing Checks

Use this element if needed to provide information about the types of checks and operations that have been performed on the data file to make sure that the data are as correct as possible, e.g. consistency checking, wildcode checking, etc. Note that the information included here should be specific to the data file. Information about data processing checks that have been carried out on the data collection (study) as a whole should be provided in the “Data editing” element at the study level.

You may also provide here a reference to an external resource that contains the specifications for the data processing checks (that same information may be provided also in the “Data Editing” filed in the Study Description section).

Files Notes This field, aiming to provide information to the user on items not covered elsewhere, will in most cases be left empty.

5.4. Good practices for completing the Variables Description

The Variable Description is the section of the DDI document that provides detailed information on each variable.

VARIABLES
Names These are the names given to the variables. Ideally, the variable names should be a maximum of 8 characters, and use a logical naming convention (e.g., section (S) and question (Q) numbers to name the question). If the variable names do not follow these principles, DO NOT CHANGE THE VARIABLE NAMES IN THE EDITOR, but make recommendations to the data processor for consideration for future surveys.
Labels

All variables should have a label that

  • Provides the item or question number in the original data collection instrument (unless item number serves as the variable name)
  • Provides a clear indication of what the variable contains
  • Provides an indication of whether the variable is constructed from other items

Recommendations:

  • Do not use ALL CAPS in labels.
  • Make sure that different variables have different labels (avoid duplicate labels).
  • For expenditure or income: indicating the currency and period of reference is crucial (e.g. “Annual per capita real expenditure in local currency”
Width, StartCol, Endcol When you import your data files from Stata or SPSS, the information on StartCol and EndCol will be empty. It is crucial to add this information, in order to allow users to export the data to ASCII fixed format. To do so, use the “Variables > Resequence” function in the Editor, for each data file.
Data type

Four types of variables are recognized by the Editot:

  • Numeric: Numeric variables are used to store any number, integer or floating point (decimals).
  • Fixed string: A fixed string variable has a predefined length (default length is 8 but it can range from 1 to 255 characters in length) which enables the publisher to handle this data type more efficiently.
  • Dynamic string: Dynamic string variables can be used to store open-ended questions.
  • Date: date variables stored in ISO format (YYYY-MM-DD?—should specify)

The data type is usually properly identified when the data is imported. It is important to avoid the use of string variables when this is not absolutely needed. Such issues must be taken care of before the data is imported in the Editor. See the section on “1. Gathering and preparing the dataset” above.

Measure

The Metadata Editor will allow you to define the measure of a variable as:

  • Nominal: variable with numeric assignations for responses; the number assigned to each response does not have a meaning by itself.
Example:
Variable sex: 1 = Male, 2 = Female (the number does not have a meaning by itself; we could as well have assigned Male = 2 and Female = 1). When variables are nominal, we can produce frequency tables by code, but calculating mean or standard deviation of the codes would not make sense.
  • Ordinal: variable with numeric assignations and in a logical sequence. The absolute size of the number, or the difference between two numbers has no meaning. But the sequence of the number matters.
Example:
An example of an ordinal variable would be a variable indicating the level of satisfaction of the respondent, for example on a scale of 1 (very unsatisfied) to 5 (very satisfied).
  • Scale: continuous variables that have inherent and not categorical value. Examples of such variables include the age of the person, the amount of income or expenditure, etc.
CATEGORIES
Categories

Variable categories are the lists of codes (and their meaning) that apply to the variable. The Editor imports categories and their labels from the source data files (SPSS, Stata).

If necessary, add/edit the codes. Use the Documentation > Create categories from statistics if the source dataset did not include value labels (e,g., when imported from ASCII). Do not include codes for “Missing”. The codes for Missing must be specified in the “Missing data” field. If you fail to do that, the summary statistics (mean, standard deviation, etc) will be calculated including the missing code, which will be considered as a valid value.

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VARIABLE INFORMATION
Time variable This is a check-box used to tag and identify variables used to define time.

Min

Max

Allows modifying the minimum value of a variable. For each variable where it makes sense, you should check that the Min and Max values are correct. Remember: if a specific value is used for “Missing”, this should not be included in the Min-Max range. For example, if codes 1 and 2 are used for Male and Female, and 9 for unknown sex, then the Min will be 1 and the Max will be 2. The code 9 must be listed in the “Missing” codes (see below).
Decimals Defines the number of decimal places of a numeric variable type.
Implicit decimals This check box is selected only when a fixed ASCII-type file is imported and the data file includes a decimal character. As the decimal character also requires a space in the variable length assignation, it is important to check this box in order to assure proper alignment of the data.
Missing data Missing values are those values that are blank in a data file but should have been responses and are within the path or universe of the questionnaire. Missing values should always be coded. Missing values should be differentiated from “not applicable” and zero (0) values.
STATISTICS
Statistics Options

Various options exist for displaying and presenting summary information of the variable to the user or the person browsing the output. Summary statistics are saved in the DDI document and become part of the metadata. It is therefore important to select the appropriate ones.

  • For nominal variables you want to be sure that the categories are well defined and that some of the summary statistics are not displayed (such as means and standard deviations.
  • For ordinal values, you want to be sure that the categories are displayed if they are required. Not all ordinal values will require a category. In some cases you may want to include some summary statistics such as mean and standard deviation.
  • For scale values, you do not want to define categories and you may want to include some summary statistics such as mean and standard deviation.

Make sure you do not include “Frequencies” for variables such as the household identification number or enumeration area. This would produce a useless frequency table, that would considerably increase the size of your DDI file (in general, a very large DDI file–8 to 10Mb or more– indicates such a problem).

Make sure also that you do not include meaningless summary statistics, such as the mean or standard deviation calculated on the codes used for variable SEX.

Notes:

  • Summary statistics such as the mean or standard deviation are calculated using all valid values. If special codes are used to indicate missing values, make sure they are declared in the “Missing” section. If not, they will be included in the calculations. For example, if you use code 99999 for indicating missing values in a variable on household expenditure, code 99999 must be listed in the missing section as follows:
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  • If you modify information such as the categories or missing values, you must use the “Documentation > Update Statistics” command in the Editor to refresh the summary statistics.
DOCUMENTATION
Definition

This element provides a space to describe the variable in detail. Not all variables require definition. The following variables should always be defined when available in a questionnaire:

  • Household (attach this definition to the “household ID” variable
  • Head of household (attach this definition to the variable “relationship to the head”
  • Urban/rural
Universe

The universe at the variable level reflects skip patterns within-records in a questionnaire. This information can typically be copy/pasted from the survey questionnaire. Try to be as specific as possible. This information is very useful for the analyst.

In many cases, a block of variables will have the same universe (for example, a block of variables on education can all relate to the “Population aged 6 to 24 year). The Toolkit allows you to select multiple variables and enter the universe information to all variables at once.

Source of information

Enter information regarding who provided the information contained within the variable. In most cases, the source will be “Head of household” or “Household member”. But it may also be:

  • GPS measure (for geographic position)
  • Interviewer’s visual observation (for type of dwelling)
  • Best informant in community
  • Etc.
Concepts

Greater description on the nature of the variable can be placed in this element. For example, this element can provide a clearer definition for certain variables (i.e. a variable that provides information on whether a person is a household member). In the case of household membership, a conceptual definition can be provided.

Example:
A household member is defined as any person who has been resident in the household for six months or more in a given year and takes meals together OR by default the head of household, infants under 6 months, newly wedded couples etc.

Pre-question text

Literal question

Post-question text

The pre-question texts are the instructions provided to the interviewers and printed in the questionnaire before the literal question. This does not apply to all variables. Do not confuse this with instructions provided in the interviewer’s manual. With this and the next two fields, one should be able to understand how the question was asked during the interview. See example below.

The literal question is the full text of the questionnaire as the enumerator is expected to ask it when conducting the interview. This does not apply to all variables (it does not apply to derived variables).

The post-question texts are instructions provided to the interviewers, printed in the questionnaire after the literal question. Post-question can be used to enter information on skips provided in the questionnaire. This does not apply to all variables. Do not confuse this with instructions provided in the interviewer’s manual. With this and the next two fields, one should be able to understand how the question was asked during the interview. See example above.

Example:
In the example below (extracted from a UNICEF-MICS standard questionnaire), we find a pre-question, a literal question and a post-question.
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  • Pre-question: Check age. If child is 3 years old or more, ask:
  • Literal question: Does (name) attend any organized learning or early childhood education programme, such as private or government facility, including kindergarten or community child care?
  • Post-question: If answer is 2 or 9 > Goto next module
Interviewer Instruction Copy/paste the instructions provided to the interviewers in the interviewer’s manual. In cases where some instructions relate to multiple variables, repeat the information in all variables. The Editor allows you to select multiple variables and enter the information to all these variables at once.
Imputation The field is provided to record any imputation or replacement technique used to correct inconsistent or unreasonable data. It is recommended that this field provide a summary of what was done and include a reference to a file in the external resources section.
Recoding and derivation

This element applies to data that were obtained by recoding collected variables, or by calculating new variables that were not directly obtained from data collection. It is very important to properly document such variables. Poorly documented variables cannot (or should not) be used by researchers. In cases where the recoding or derivation method was very simple, a full description can be provided here. For example, if variable AGE_GRP was obtained by recoding variable S1Q3, we could simply mention “Variable obtained by recoding the age in years provided in variable S1Q3 into age groups for years 0-4, 5-9, …, 60-64, 65 and over. Code 99 indicates unknown age.”

When the derivation method is more complex, provide here a reference to a document (and/or computer program) to be provided as an External Resource. This will be the case for example for a variable “TOT_EXP” containing the household annual total expenditure, obtained from a household budget survey. In such case, the information provided here could be:

“This variable provides the annual household expenditure. It was obtained by aggregating expenditure data on all goods and services, available in sections 4 to 6 of the household questionnaire. It contains imputed rental values for owner-occupied dwellings. The values have been deflated by a regional price deflator available in variable REG_DEF”. All values are in local currency. Outliers have been fixed. Details on the calculations are available in Appendix 2 of the Report on Data Processing, and in the Stata program “aggregates.do” available in external resources.”

Security This field will be left empty in most cases. It can be used to identify variables that are direct identifiers of the respondents (or highly identifying indirect identifiers), and that should not be released.
Notes This element is provided in order to record any additional or auxiliary information related to the specific variable.

5.5. Good practices for completing the External Resources description

The External Resources are all materials related to the study others than the data files. They include documents (such as the questionnaires, interviewer’s manuals, reports, etc), programs (data entry, editing, tabulation, and analysis), maps, photos, and others. To document external resources, the Metadata Editor uses the Dublin Core metadata standard (which complements the DDI standard).

Label This is the label that will be used to display a hyper link to the attached document. It can be the title, name, or an abbreviated version of the title.
Resource The resource is used to point to the file that will be attached and distributed. The folder where the document is found is a relative path and should be the folder that will be pasted into the document path. Once you have pointed to the specified resource make sure you check file access by clicking the folder icon to the right of the entry field.
Type

This is crucial information. A controlled vocabulary is provided. The selection of the type is important as it determines the way it will be presented or displayed to the user in the final output. The following are the choices:

  • Document Administrative: This includes materials such as the survey budget; grant agreement with sponsors; list of staff and interviewers, etc.
  • Document Analytical: Documents that present analytical output (academic papers, etc. This does not include the descriptive survey report (see below).
  • Document Questionnaire: the actual questionnaire(s) used in the field.
  • Document Reference: Any reference documents that are not directly related to the specific dataset, but that provide background information regarding methodology, etc. For international standard surveys, this may for example include the generic guidelines provided by the survey sponsor.
  • Document Report: Survey reports, studies and other reports that use the data as the basis for their findings.
  • Document Technical: Methodological documents related to survey design, interviewer’s and supervisor’s manuals, editing specifications, data entry operator’s manual, tabulation and analysis plan, etc.
  • Document Other: Miscellaneous items
  • Audio: audio type files.
  • Map: Any cartographic information.
  • Photo: Photos can provide good documentary evidence of a survey.
  • Program: programs generated during data entry and analysis (data entry, editing, tabulation and analysis). These can be zipped together (include a brief summary report to describe the contents)
  • Table: Tabulations such as confidence intervals that may not be included in a general report.
  • Video: video type files provided as additional visual information
  • Website: Link to related website(s), such as a link to a Redatam server, or to the website of the survey sponsor in the case of international survey programs like the DHS, LSMS, or MICS).
  • Database: any databases related to the survey (e.g., a Devinfo database providing the aggregated results of the survey).
Title Full title of the document as it is provided on the cover page.
Subtitle Subtitle if relevant.
Author(s) Include all authors that are listed on the report.
Date Created Date of the publication of the report or resource (at least month and year). For reports, this is most likely stated on the cover page of the document. For other types of resources, put here the date the resource was produced.
Country The country (or countries) that are covered by the associated document.
Language Use the Language element to list all languages which appear in a resource. The languages should be selected from the drop-down list, and each language should appear on its own line. The proposed controlled vocabulary is based on ISO 639-3s.
Format The file format provides information on the kind of electronic document being provided. This includes: PDF, Word, Excel etc. This is a controlled vocabulary. If the controlled vocabulary does not provide the format you need, type it (or add it in the controlled vocabulary using the Editor Template Editor). Providing information on the format will inform the user on the software needed to open the file.
ID Number If there is a unique ID number which references the document (such as a Library of Congress number or a World Bank Publication number) include this as the ID Number.
Contributor(s) Include the names of all organizations that have been involved or contributed to producing the publication. This included funding sources as well as authoring entities.
Publisher(s) Include the official organization(s) accredited with disseminating the report.
Rights Some resources are protected by copyrights. Use the Rights element to provide a clear and complete description of the usage rights if relevant.
Description A brief description of the resource.
Abstract An abstract of the content of the resource.
Table of Contents Use the Table of Contents element to list all sections of a report, questionnaire, or other document. When copying a table of contents from another file into a project, pay close attention to the formatting as tabs, indents, and fonts may not be preserved. Because the text cannot be formatted, adopting strategies such as placing chapter titles in capital letters can help keep a table of contents organized. Including page numbers is not crucial.
Subjects The key topics discussed in the resource can be listed in the Subjects element. Although the IHSN Resource Template does not include a controlled vocabulary for this element, organizations may opt to modify the template and establish a set list of subjects which all of their projects should use when documenting studies.

6. Creating variable groups

Variable groups are optional, but will help organize the data for the user into specific subject of use categories. This will be particularly useful to the user in the case of data files that contain many variables and are not organized by topic (some flat files contain hundreds or even thousands of variables).

The Metadata Editor allows you to group variables found in various separate data files. For example, education data may be found in various locations and the disparate variables grouped together. Also, a same variable can belong to more than one group.

Variable groups are “virtual”. The variables themselves are not moved or grouped. They remain untouched in the data files.

The variable groups will appear under a menu item “Data dictionary”. The only reason for grouping variables is to allow users to easily locate variables related to their topic of interest. If your dataset contains very few variables, there is no justification for grouping them.

If you decide to create variable groups (and sub-groups if needed), make sure that ALL variables in the dataset belong to at least one group.

Variable groups also have their own DDI elements which include Type, Label, Text, Definition, Universe, and Notes. These elements are optional and will in most cases be left empty.

Type This is a controlled vocabulary field. It best identifies the manner the variables are grouped together. This field is optional.
Label The label used to identify the group should be clear and relate to the type chosen. If these are grouped by subject, then the subject should be clearly stated etc.
Text Include additional text to clarify the reason or purpose for grouping the variables. This field is optional.
Definition This optional field is used to define the variable group.
Universe This optional field defines the universe relevant to the selected grouped variables. The variables for example can be grouped as “Fertility Data” and the universe restricted to women between the ages of 15-49.
Notes Additional space for further optional explanatory notes.

7. Running validations and diagnostics

The Metadata Editor includes a useful series of diagnostic and validation modules (see the drop down menu Tools): these range from very simple validations (such as the Tools-Validate Metadata) to complex visual displays that iterate through each variable and provides feedback to the archivist at the variable level.

  • Validate Metadata: verifies that all mandatory fields are filled in.
  • Validate External Resources: verifies all mandatory fields in the External Resources are filled in.
  • Health Check: displays a popup window that provides some information and diagnostics regarding the R package. The Metadata Editor uses R to import and export the data. The health check option tells the which version of R is being used on the machine. In addition, the Health Check will provide information on the Environment Path and the result of the execution of the R script.
  • Validate Dataset Relations: this option is used to validate hierarchically related datasets. The ‘Base key variables’ should be the variables that uniquely identify a case within that file.
  • Translation Manager: provides the user with the ability to translate the interface of the Metadata Editor into any language. Selecting this option will display the Translation Manager interface. When using the option for the first time, the English template will be displayed with all the labels that require translation.

In addition to these validations, it is recommended that you generate the DDI document (in the Editor, use the Export DDI” function) and verify the size of the resulting [.xml] file. A fully documented survey with a large number of variables should not produce a file larger than 10Mb. Very large DDI files often indicate errors in the selection of summary statistics (for example, frequencies are produced for a variable like the household ID in a sample household file).

8. Generating the survey documentation in PDF

Once you are confident that all necessary checks have been completed, you may generate the survey documentation in PDF. The Metadata Editor includes a useful tool for producing a PDF document summarizing all metadata entered in the Editor (see Documentation > PDF Documentation). Generating this report is one of the final stages of properly preparing a survey for publication and dissemination. If previous versions exist and changes have been made to the data files or the metadata make sure you re-run the PDF generator.

This report should be generated, saved and attached as an External Resource.

!
The PDF report will include a list of all external resources related to the study. This list should include this PDF report itself. Before you generate it, make sure you create one entry in the External Resources for documenting this report. Immediately after you generate the PDF report, import it in the Editor.

One thing to keep in mind is that in a survey with a large number of variables may produce a document that is very long. If the report is in excess of 300 or 350 pages, you may want to split this report (e.g., produce one report with the study metadata, and one with the files and variables metadata), or change the content options (e.g., not including a frequency table for all variables).

If your agency has a website, you may upload this PDF directly to the web server. The IHSN recommends the use of a proper DDI-compliant cataloguing system, such as the one provided by its National Data Archive (NADA) application. NADA is an open source package, available free of charge at www.surveynetwork.org.

9. Independent quality review

An independent review of the data and metadata is highly recommended prior to publishing the final output. The Appendix provides a blank review form (the DDI Reviewer’s Feedback Form) to be used by an external reviewer.

The external review can be based on:

  1. The DDI file (xml file, containing no microdata and no external resources)
  2. The Metadata Editor project (containing microdata and DDI/DCMI metadata)
  3. The PDF Document
  4. The Microdata

The preferred option is to review the metadata and microdata, as it allows a full check of the final output. If data are highly confidential and cannot be shared with the reviewer, options 1-3 are the most appropriate.

In order to prepare for the independent quality review, proceed to step 10 if you will use options three or four. Follow the guidance there, and then finalize the archiving before producing the final output. Else, send the DDI-XML to the reviewer.

Section A . Data Validations in Stata: Practical Examples

Example 1 . Check for unique identifiers (single variable)

This example uses a Country Opinion Survey and uses the Stata command -isid- to check whether the variable “id” uniquely identifies the observations. Each row of the data represents a different Country’s Stakeholders and the variable that identifies each one is named “id”.

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If, after running the -isid- command you have not got an error message, it indicates that the “id” is unique and identifies each unit of analysis.

Example 2 . Check for unique identifiers (single variable)

For this example, we use the same data than Example 1, but in this case, there are some hypothetical observations with the same values for the variable “id”. The highlight observations are the duplicates IDs.

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Since there are not unique IDs in the data, it is also useful to see the list of all duplicates. To do that, we can use the Stata command -duplicates list-.

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Example 3 . Check for unique identifiers (ID made of multiple variables)

The Multiple Indicator Cluster Survey at Women-level data is used in this example. According to the study’s metadata, the unique identification of each woman is the combination of variables HH1 (Cluster Number), HH2 (Household Number) and Ln (Line Number of women), so instead of checking the unique identifier in just one variable, we are checking this condition in this group of variables.

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After running this validation, it is possible to see that the combination of “HH1”, “HH2” and “ln” generates a unique ID.

Example 4 . Check for duplicate observations

This example uses the dataset mentioned in example 2, in which there are 3 duplicated identifiers.

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As shown, 446 records are unique in the database, but there are six observations for which there are two copies of each one. Now, it is necessary to identify duplicates. The code below allows one to generate a variable that tags the duplicates with a value 1 or more, depending on the number of times a record is duplicated.

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The table above shows that records with the IDs 101, 104 and 111 each have one duplicate.

Example 5 . Check the merge between datafiles

The code below helps us combine the data collected at the individual-level with the data collected at the household-level. In this case, we have two hierarchical datasets, in the household data each row represents one household, and each household has members or individuals. So, we need to combine many observations from one data set (individual-level) with one observation from the other (household-level). The ID of the household data set is the unique identifier that we are using for the merge (“HH1”and “HH2”).

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The report shows that all observations in the Individual file have a corresponding household in the household data set and that all households have at least one member. However, let’s consider a hypothetical example that contains some records that do not match, below the results of the merge:

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The merge command resulted in: 15 nonmatched observations originated from the master data and 2 from the using data. The inconsistencies between databases could be the result of a data entry error or processing errors and these also need to be referred to the data producer before documentation begins.

Example 6 . Check variables full of missing values

In the example above, there are 3 variables (WM1_1, WM3_1 and WM5_1) full of missing values. As shown in the table, the -misstable summarize- command allows one to identify all those cases at once. It is like tabulating every single variable to identify missing values but more efficiently.

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Example 7 . Check the completeness of the data files

This example shows how you can check for discrepancies (if any) between the variables from the MICS women’s questionnaire and the data set.

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As shown, this dataset contains all variables from the section “Woman’s background,” and they are organized according to the questionnaire. The comparison between variables in the questionnaire to those in the data set should be made for every section in the questionnaire.

Example 8 . Check all variables are labelled

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The following Form is available at www.surveynetwork.org

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[1]DDI (Data Documentation Initiative) and DCMI (Dublin Core Metadata Initiative) are international XML metadata specifications. For more information on these standards and on the IHSN Toolkit, please visit www.surveynetwork.org.
[2]See section 3 – Importing data and establishing relationships for more information on key variables.
[3]In Stata, this can be done through the use of the group function from the egen command. For example, to create a variable hhid based on a combination of variables province, district, ea and hhnum, use the command “egen hhid=group(province district ea hh_num )”.