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Evaluation of the Magnitude of Differential Item Functioning in Polytomous Items DIF

Thayer, Dorothy T.; Zwick, Rebecca J.
Publication Year:
Report Number:
ETS Research Report
Document Type:
Page Count:
Subject/Key Words:
Differential Item Functioning (DIF), Mantel-Haenszel Technique, Standard Error of Measurement, Statistical Inference, Test Items


Several recent studies have investigated the application of statistical inference procedures to the analysis of differential item functioning (DIF) in test items that are scored on an ordinal scale. Mantel's extension of the Mantel-Haenszel test is a possible hypothesis-testing method for this purpose. The development of descriptive statistics for characterizing DIF in polytomous test items has received less attention. A statistic that appears well-suited as a summary index was proposed by Dorans and Schmitt. In this paper, two possible standard error formulas for this statistic are derived and evaluated, hypothesis testing procedures based directly on this descriptive statistic are outlined, and the results of applications to simulated data area presented. (30pp.)

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