A manipulation check is defined as a measure used to determined whether an independent variable in a social science study varies in ways researchers expect, according to McGraw-Hill. For instance, participants can be tested on their recall abilities by asking them questions about some important aspect of the experiment they witnessed. Another way to check for manipulation is to put questions in a survey that mark whether someone pays attention.
Manipulation checks ensure the experiment is valid, and no subjects falsified the results. Another way to check whether or not subjects paid attention revolves around expected variations. If someone shows a video about violent crime, scientists expect respondents in that group to have some negative reactions. When a study shows pictures of fluffy rabbits and pristine nature scenes, researchers expect the reactions of participants in this group to be positive.
In pure surveys with multiple choice questions, a manipulation check is done by putting a few nonstandard questions in the mix. A survey can say, "Please mark 'mostly positive' for this question." Another question can reveal, "Please answer 'no difference' for this blank."
A manipulation check is used in psychological and sociological studies. The studies can involve hands-on research, surveys or questionnaires, or a combination of techniques. The independent variable does not depend upon other variables in the study.