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	Differential Item Functioning in Educational Testing	項目応答理論 (IRT)
分野	Education	心理測定学
系統	Latent structure	Latent structure
提唱年	1993	1952–1968
提唱者	Educational measurement / test-fairness tradition (Holland, Wainer, Dorans, Thissen)	Frederic M. Lord (and Allan Birnbaum for the 2PL/3PL models)
種類	Test-fairness analysis detecting items that function differently across groups	Probabilistic measurement model
原典	Holland, P. W., & Wainer, H. (Eds.). (1993). Differential Item Functioning. Lawrence Erlbaum Associates. ISBN: 9780805809725	Lord, F. M. & Novick, M. R. (1968). Statistical Theories of Mental Test Scores. Addison-Wesley.
別名	Educational DIF Analysis, Item Bias Detection in Tests, Test Fairness DIF, Mantel-Haenszel DIF	IRT, latent trait theory, item characteristic curve theory, modern test theory
関連	4	5
概要	Differential item functioning (DIF) analysis is the central statistical tool for evaluating the fairness of test items in education. An item shows DIF when examinees of equal ability but different group membership — for example by gender, race/ethnicity, or language background — have unequal probabilities of answering it correctly. By conditioning on ability before comparing groups, DIF analysis separates genuine item bias from real group differences in proficiency, and flags items for expert review before they affect high-stakes decisions.	Item response theory models the probability that a respondent answers an item correctly (or endorses it) as a function of the respondent's latent trait level and the item's own statistical properties — difficulty, discrimination, and guessing. Unlike classical test theory, IRT places persons and items on the same scale, yielding measurement that is sample-independent for items and test-independent for persons.