IDENTIFICATION OF NONUNIFORM DIFFERENTIAL ITEM FUNCTIONING USING A VARIATION OF THE MANTEL-HAENSZEL PROCEDURE

The Mantel-Haenszel (MH) procedure has become one of the most popular procedures for detecting differential item functioning (DIF). One of the most troublesome criticisms of this procedure is that whereas detection rates for uniform DIF are very good, the procedure is not sensitive to nonuniform DIF. In this study, examinee responses were generated to simulate both uniform and nonuniform DIF. A standard MH procedure was used first. Then, examinees were split into two samples by breaking the full sample at approximately the middle of the test score distribution. The tests were then reanalyzed, first with the low-performing sample and then with the high-performing sample. This variation improved detection rates of nonuniform DIF considerably over the total sample procedure without increasing the Type I error rate. Items with the largest differences in discrimination and difficulty parameters were most likely to be identified.