Analysis of differential item functioning in translated assessment instruments

The usefulness of three IRT-based methods and the Mantel-Haenszel technique in evaluating the measurement equivalence of translated assessment instruments was investigated. A 15-item numerical test and an 18-item reasoning test that were originally developed in English and then translated to French were used. The analyses were based on four groups, each containing 1,000 examinees. Two groups of English-speaking examinees were administered the English version of the tests; the other two were French-speaking examinees who were administered the French version of the tests. The percent of items identified with significant differential item functioning (DIF) in this study was similar to findings in previous large-sample studies. The four DIF methods showed substantial consistency in identifying items with significant DIF when replicated. Suggestions for future research are provided. Index terms: area measures, differential item functioning, item response theory, language translations, Lord’s X², Mantel-Haenszel procedure