An Analytical Evaluation of Two Common-Odds Ratios as Population Indicators of DIF.Report as inadecuate

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The Mantel-Haenszel (MH) statistic for identifying differential item functioning (DIF) commonly conditions on the observed test score as a surrogate for conditioning on latent ability. When the comparison group distributions are not completely overlapping (i.e., are incongruent), the observed score represents different levels of latent ability across groups, and observed score conditioning may be ineffective. In this study, MH common-odds ratios conditioned on observed score and latent ability were evaluated as population indicators of DIF. The performances of the MH common-odds ratios were compared on moderate to high difficulty tests for combinations of degree of distributional incongruence, test length, occurrence of DIF, and ratio of examinees in the comparison groups. Under all conditions, the observed score and latent ability MH common-odds ratios performed similarly, even with fairly incongruent distributions. This provides reassurance in conditioning on observed score when the MH statistic is applied to large finite samples with incongruent group distributions. (Contains seven references, five tables, and two figures.) (Author)

Descriptors: Ability, Comparative Analysis, Difficulty Level, Item Bias, Raw Scores, Sample Size, Statistical Distributions, Test Items, Test Length

ACT Research Report Series, P.O. Box 168, Iowa City, IA 52243.

Author: Pommerich, Mary; And Others


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