Detection of Differential Item Functioning in Dichotomous and Polytomous Items: The Exploratory Correspondence Analysis Method
Differential item functioning (DIF) has emerged as a field of study within psychometrics, focusing on detecting items in tests and scales that perform differently for different groups while controlling for ability (Holland and Thayer, 1988). Detection of DIF starts with the assumption that individuals of the same ability or trait level should respond to a given item similarly. When we find that respondents with the same ability level from different groups (e.g. racial groups, socio-economic groups, different primary languages) consistently provide different responses, we suspect that the item has properties that affect how the group members interpret the item. For example, there may be cultural references, specialized language, levels of exposure, or anynumber of reasons why one group may understand or interpret an item differently from another group. The process of detecting these differences, identifying the magnitude of the differences, and determining whether these differences are likely due to chance is what psychometricians broadly term differential item functioning.
Grochowalski, Joseph H, "Detection of Differential Item Functioning in Dichotomous and Polytomous Items: The Exploratory Correspondence Analysis Method" (2013). ETD Collection for Fordham University. AAI13853031.