Back Checks

Back checks are an important tool that allows the research team to verify the quality and validity of survey data. Throughout the duration of the fieldwork, a back check team returns to a randomly-selected sub-sample of households who have already been interviewed by enumerators. The back check team re-interviews these respondents, using a much smaller set of questions from the actual survey instrument (or questionnaire). This is known as a back check survey, and allows the research team to modify certain aspects of the data collection to improve data quality.

Read First

• Back checks are an important tool to detect fraud, for instance, enumerators filling out questionnaires themselves.
• Back checks help researchers to assess the accuracy of data collection, and monitor data quality.
• Back checks can be conducted by in-person visits, or through phone calls. A complementary approach to in-person back checks is conducting random audio audits.
• Back checks allow the research team to resolve issues in data collection by improving enumerator training , or replacing low-performing or problematic enumerators.

Logistics

• Duration. The total duration of each back check survey should be around 10-15 minutes.
• Specialized enumerators. Hire a team of experienced and skilled enumerators to conduct the back checks.
• Independent team. The back check team should be independent from the rest of the survey staff. Train them separately, and ensure that there is very little or no contact between the back check team and the survey team.
• 20%-First 2 Weeks rule. Administer 20% of back checks within the first two weeks of fieldwork. This helps the research team to identify quickly whether the questionnaire is effective, whether enumerators are doing their jobs well, and what changes to make to ensure high quality data collection.

Sampling

The following points are important when selecting the sample for the back check survey:

• Sample size. Aim to back check 10-20% of the total observations.
• Stratified sampling. The back check sample should be stratified, that is it must cover all survey teams and enumerators. Back check every team, and every enumerator regularly, and as frequently as possible.
• Include missing respondents. This is to verify that there is no bias in the sample just because enumerators did not track hard-to-find respondents.
• Include other flagged observations. Include observations that were flagged in other quality tests like high frequency checks. Also include respondents who were interviewed by enumerators suspected of cheating.

Designing the Back Check Survey

Questions for the back check survey (or simply back check) are drawn from the actual questionnaire which is used for data collection. There are five types of questions that should be included in a back check to get a clear idea of the data quality, as well as the enumerator's skills:

• Questions to verify respondent and interview information: Verify the identity of the respondent and check if, when, and where the original survey took place. Useful for verifying reported completion rates.

• Questions to detect fraud: Questions that ask for straightforward information which has no expected variation or room for error. They do not require particularly skilled enumerators, and do not vary over time - especially the time period between the actual interview and the back check. For example, questions about type of dwelling, education level, marital status, occupation etc. The actual questions in this category will depend on the survey instrument and context. If the answers to these questions differ between the actual survey and the backcheck survey, it is a sign of either poor data quality, a serious enumerator problem, and/or potential wrongdoing by the enumerator.

• Questions to detect errors in survey execution: Questions that have complex loops or skip patterns, or check for consistency of recorded answers. For example, if household size is recorded as 4, then the number of repeat groups for household members should not be more than 4. Capable enumerators should get the true answer for these questions. If values for these questions differ between the questionnaire and the backcheck survey, then the enumerator may need more training.

• Questions to detect problems with the questionnaire or key outcomes: Provide additional checks for accuracy, and flag difficulties and/or inconsistencies in the interpretation of the questions by enumerators. If these values differ between the actual survey and the back check, then the enumerator may need more traning. In some cases, the survey instrument may need to be simplified.

• Questions that repeat multiple times: Check whether enumerators are falsifying data to reduce the length of interviews. For example, if there is a long series of questions about each household member, verify that the number of times these questions repeat is equal to the number of household members.

Note that it is important that enumerators do not know what questions will be included in the back check survey. To do so, you may consider randomizing questions, or changing the back check survey regularly during data collection.

bcstats

After completing a back check, you can compare the back check data with the original survey data. You can do this using the Stata command bcstats, developed by Innovations for Poverty Action. This command produces a dataset that lists the comparisons between the back check and original survey data. The command also allows research teams to perform enumerator checks and stability checks for variables. The results produced by IPA are categorized into 3 types, which is slightly broader than the classification we explained above.

The following syntax is used for performing back checks using bcstats:

ssc install bcstats 
bcstats, //
  surveydata(filename) bcdata(filename) id(varlist)//
  [options]

To learn in more detail about the options for bcstats and back checks, please type help bcstats on Stata after installing the command. Listed below are two options that are used most commonly with bcstats.

Comparing different variable types

As part of the functionalities under [options], bcstats allows users to compare 3 different types of variables.

• t1vars(): Specifies the list of type 1 variables. These are variables that are expected to stay constant between the survey data and the back check. In case there are differences for these variables, the research team may take action against the enumerator. This option displays variables which have high error rates, and variables with completed the enumerator checks. This includes Questions to verify respondent and interview information, Questions to detect fraud and Questions that repeat multiple times.

• t2vars(): Specifies the list of type 2 variables. These are variables that may be difficult for enumerators to work with. For instance, they may involve complicated skip patterns or complex logic. In this case, if there are differences between the survey data and the back check, it may indicate the need for further training, but will not result in action against the enumerator. This option displays the error rates for these variables, and variables with completed enumerator checks and stability checks. This includes Questions to detect errors in survey execution.

• t3vars(): Specifies the list of type 3 variables. These are variables whose stability between the survey and back check is of interest to the research team. If there are any differences for these variables between the survey data and back check data, it will not result in action against the enumerator. This option displays the error rates of all variables, and variables with completed stability checks. This includes Questions to detect problems with the questionnaire or key outcomes.

Stability

bcstats also allows users to test for stability by running a paired t-test to compare the sample means for the survey data and the back check data. It also allows users to specify the confidence level for the t-test using the level() option. By default, it considers a 95% confidence level.

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This article is part of the topic Field Management.

Additional Resources

• DIME Analytics (World Bank), Assuring Data Quality
• DIME Analytics (World Bank), Field Data Quality Validation
• World Health Organization's Quality Assurance in Surveys: standards, guidelines, and procedures.
• bcstats, a Stata program written by an IPA staff member for conducting back checks on survey data.