Abstract
The Mantel-Haenszel (MH) procedure (Mantel and Haenszel) is a popular method for estimating and testing a common two-factor association parameter in a 2 × 2 × K table. Holland and Holland and Thayer described how to use the procedure to detect differential item functioning (DIF) for tests with dichotomously scored items. Wang, Bradlow, Wainer, and Muller showed that the MH procedure unexpectedly often found DIF where there was none for very easy items. They showed that their suggested Bayesian procedure for DIF detection did not have the same problem. We discuss a simpler solution of the problem—the use of the standardized difference in proportion correct (STD P-DIF) procedure in conjugation with the MH procedure—that has been used by DIF analysts since 1988. We also show, using results from real and simulated data, that it is possible to overcome the problem using the empirical Bayes (EB) procedure of Zwick, Thayer, and Lewis, which also is computationally simpler than the procedure suggested by Wang et al.
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