There are two main types of missing data that are seen in social science research:
- Item nonresponse happens when a respondent fails to complete part of a survey, questionnaire, or test.
- There can be many reasons for item nonresponse. For example, item nonresponse can occur:
- Just by chance, perhaps the respondent didn’t see the item.
- If the respondent isn’t sure how to answer an item or chooses not to answer.
- If an item is skipped during the collection process or because of some research equipment malfunction
- There can be many reasons for item nonresponse. For example, item nonresponse can occur:
- Wave nonresponse applies to longitudinal research where data are collected at different time points (waves) and data is not collected for a respondent for an entire wave.
- Wave nonresponse can happen because:
- A participant was unable to participate in a data collection wave, but comes back for subsequent waves
- A participant dropped out of the study (attrition)
- Wave nonresponse can happen because:
Click on the image below to see an illustration of the types of missing data.
