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	ポリトマス項目分析	Graded Response Model (GRM)
分野	心理測定学	心理測定学
系統	Latent structure	Latent structure
提唱年	1969–1982	1969
提唱者	Fumiko Samejima (graded response model, 1969); David Andrich (rating scale model, 1978); Geoffrey Masters (partial credit model, 1982)	Fumiko Samejima
種類	Item-level psychometric analysis	Item response theory / polytomous IRT model
原典	Samejima, F. (1969). Estimation of latent ability using a response pattern of graded scores. Psychometrika Monograph Supplement, 34(4, Pt. 2), 1–97.	Samejima, F. (1969). Estimation of Latent Ability Using a Response Pattern of Graded Scores. Psychometrika Monograph Supplement, No. 17.
別名	ordered-category item analysis, graded response analysis, polytomous IRT, rated-scale item analysis	Samejima's GRM, Derecelendirilmiş Tepki Modeli (GRM), graded IRT model
関連	4	7
概要	Polytomous item analysis examines the psychometric behavior of items that have more than two ordered response categories — such as Likert-type scales or partial-credit tasks. It evaluates each item's difficulty thresholds, discriminating power, and category functioning to determine whether the full response scale is being used as intended and whether each item contributes reliably to measuring the underlying construct.	The Graded Response Model is an item response theory model developed by Fumiko Samejima in 1969 for ordered polytomous items such as Likert-type scales. It estimates both the discriminating power of each item and a set of threshold parameters marking the boundaries between adjacent response categories, while simultaneously placing persons on a continuous latent trait scale.