Examining the effects of differential item (functioning and differential) test functioning on selection decisions: When are statistically significant effects practically important?

Item response theory differential test functioning (DTF) methods are often used to address issues in personnel selection, but the results are frequently difficult to interpret because statistically significant findings may have little practical importance. In this article, the authors proposed 2 effect size measures for DTF. One related DTF to mean raw score differences across groups; the other related DTF to the 4/5th rule for adverse impact at successive cut scores. The effects of DTF were examined in the context of personality assessment, professional licensure, and college admissions. Overall, the result indicated that although many items exhibited bias in analyses of the large samples, the net magnitudes of effect on potential selection decisions were nugatory.