A comparison of Mantel-Haenszel differential item functioning parameters (LSAC Research Report 98-03

Differential item functioning (DIF) analyses are conducted to investigate how items function in various subgroups. The Mantel-Haenszel (MH) DIF statistic is used at the Law School Admission Council and other testing companies. When item functioning can be well-described in terms of a one- or two-parameter logistic item response theory (IRT) model and subgroup differences can be conceptualized as a difference in item difficulty, the MH DIF statistic can be readily understood in terms of the IRT item parameters. When items follow the three-parameter logistic IRT model, however, the relationship between MH DIF statistic and IRT is more complicated, and several competing parameters that relate the statistic to IRT parameters have been proposed. The goal of this study was to investigate various MH DIF parameters to determine which is most appropriate. The parameters were compared with the MH DIF statistic using both simulated and real data from a recent administration of the Law School Admission Test (responses of 20,092 white male test takers). Results suggest that the most appropriate parameter is the one that is theoretically most similar to the MH DIF statistic itself. (Contains 3 figures, 2 tables, and 16 references.) (Author/SLD) Reproductions supplied by EDRS are the best that can be made from the original document. 1.