Differences in Item Performance Across Groups GMAC GMAT
Sinnott, Loraine T.
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ETS Research Report
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Graduate Management Admissions Council,
Graduate Management Admission Test (GMAT),
An analysis of the Graduate Management Admission Test was undertaken to isolate factors that make some items unexpectedly easy or difficult for minority candidates relative to the majority candidate, a young male Caucasian of U.S. citizenship. Minority groups were selected within the following dimensions: sex, ethnic background or race, age, and language fluency. Fourteen pairwise group comparisons were completed and all sections of a current test form analyzed. The group comparisons were of item difficulty. An iterative technique was adopted to determine a line of best fit for plots of difficulty for one group against difficulty for another. Empirical criteria were established for identifying outlying items as unexpectedly easy or difficult. In addition to describing the study and its results, the research report includes a discussion of how the methodology may be extended to the simultaneous comparison of any number of groups and an analysis of the sampling error in calculations of item difficulty.