Differential item functioning on the Mini-Mental State Examination. An application of the Mantel-Haenszel and standardization procedures.

Differential item functioning (DIF) attempts to identify items for which subpopulations of examinees exhibit performance differentials that are not consistent with the performance differentials seen among those subpopulations on a reliable measure of the construct of interest. DIF assessment requires a rule for scoring items and a matching variable on which different subpopulations can be viewed as comparable for purposes of assessing their performance on items. Typically, DIF is operationally defined as a difference in item performance between subpopulations, eg, Spanish-speakers and English-speakers, which exist after members of the different subpopulations have been matched on some one-dimensional matching variable such as total score. This work defines DIF, describes 2 standard procedures for measuring DIF, applies these DIF procedures to the Mini-Mental State Examination, and contrasts DIF with score equity analysis (SEA). The description of DIF assessment presented in this paper is applicable to any examination question that has responses that can be ordered, eg, with respect to correctness or severity.