Differential item functioning

From LiteracyTentWiki

Differential item functioning AleAssessment

(DIF) is the statistical detection of systematic performance differences between individuals with the same underlying true ability from different groups (commonly: race/ethnicity, gender, etc.). When an item is flagged as DIF, it means that a statistical difference was found in the probability that individuals from different groups who are otherwise at the same ability level would answer that item correctly.

It is important to note that such performance differences should not be assumed to reflect bias. An item can reflect DIF for different reasons. Sometimes, though most tests conduct sensitivity and fairness reviews, an item may be inappropriate or culturally unfamiliar to one group of test-takers, and thus is not fair. On the other hand, differences in performance may reflect differences in opportunity to learn content. In that case, the test items themselves not be the fundamental problem-- rather, the occurrence of DIF highlights other issues of concern in instruction or society. 2/7/2005, April L. Zenisky.

---

Back to Assessment Glossary

Back to ALEGlossary