Differential Item Functioning
A questionnaire or test item shows differential item functioning (DIF) if the probability of responding correctly to the item differs between individuals belonging to different groups although they have been matched on the underlying latent trait.
It is essential to ensure that a test is fair to all test takers. A person’s observed item response should depend only on that person’s latent trait level, but not additionally on, for example, whether they are male or female. Whether this is the case can be investigated by testing items for DIF. Typically, DIF investigations compare items between groups (e.g., gender, age categories, or other relevant demographic variables). When no DIF is found, this indicates that the response categories of an item relate in the same way to the latent trait in the groups that were compared. This is important, since in this case manifest differences in...
KeywordsDifferential Item Functioning Item Response Theory Latent Trait Item Response Theory Model Differential Item Functioning Analysis
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