手法を比較

	一般化可能性理論（G理論）	項目応答理論 (IRT)
分野	心理測定学	心理測定学
系統	Latent structure	Latent structure
提唱年	1963–1972	1952–1968
提唱者	Lee J. Cronbach, Goldine Gleser, Harinder Nanda, Nageswari Rajaratnam	Frederic M. Lord (and Allan Birnbaum for the 2PL/3PL models)
種類	Variance-components reliability model	Probabilistic measurement model
原典	Cronbach, L. J., Gleser, G. C., Nanda, H. & Rajaratnam, N. (1972). The Dependability of Behavioral Measurements: Theory of Generalizability for Scores and Profiles. Wiley.	Lord, F. M. & Novick, M. R. (1968). Statistical Theories of Mental Test Scores. Addison-Wesley.
別名	G-theory, G-study / D-study framework, variance components reliability	IRT, latent trait theory, item characteristic curve theory, modern test theory
関連	4	5
概要	Generalizability Theory is a psychometric framework that decomposes observed score variance into multiple sources — persons, items, raters, occasions, and their interactions — using analysis of variance. It replaces the single reliability coefficient of classical test theory with a family of coefficients that tell researchers how well scores generalize across different measurement conditions.	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.