Aninstructionalmanipulation check, often abbreviatedIMC, is a special kind of question inserted in aquestionnaire among the regular questions, designed to check whether respondents are paying attention to the instructions.[2] Discarding responses by participants who fail to read the instructions increases thesignal-to-noise ratio and can thereby increase thestatistical power of an experiment. The tool was developed by Oppenheimeret al.[1]
Eliminating random responses this way before performingstatistical hypothesis testing may be considered a legitimate form ofdata manipulation, but should be duly mentioned in publications reporting on the outcome of the experiment in question.[3]
Among several forms an IMC can take, a popular one is the so-calledblue-dot task,[3] suitable foron-line questionnaires. A number of larger blue circles are arranged according to aLikert scale from (say) "very rarely" to "very frequently". Participants who ignore the instructions and merely want to finish the task will just click any one of these circles. The instructions, however, ask the participants to ignore the larger circles and instead click a little blue dot at the bottom of the screen. Oppenheimeret al. report that in a large sample ofundergraduate participants, approximately 7% failed this task.[1]
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