Differential Item Functioning (DIF) Analysis

The differential item functioning (DIF) analysis is a procedure used to determine if test questions are fair and appropriate for assessing the knowledge of various ethnic groups and females. It is based on the assumption that test takers who have similar knowledge (based on total test scores) should perform in similar ways on individual test questions regardless of their sex, race, or ethnicity. This procedure was developed in 1986 by researchers from the Educational Testing Service (ETS) and is used with many ETS tests.

For further information, refer to What's the DIF? Helping to Ensure Test Question Fairness (Educational Testing Service, 1996).