手法を比較

	ポリトマス項目分析	部分評点モデル（PCM / GPCM）
分野	心理測定学	心理測定学
系統	Latent structure	Latent structure
提唱年	1969–1982	1982
提唱者	Fumiko Samejima (graded response model, 1969); David Andrich (rating scale model, 1978); Geoffrey Masters (partial credit model, 1982)	Geoff N. Masters (PCM, 1982); Eiji Muraki (GPCM, 1992)
種類	Item-level psychometric analysis	Item Response Theory / Polytomous IRT
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.	Masters, G. N. (1982). A Rasch model for partial credit scoring. Psychometrika, 47(2), 149–174.
別名	ordered-category item analysis, graded response analysis, polytomous IRT, rated-scale item analysis	Kısmi Kredi Modeli (PCM / GPCM), Generalized Partial Credit Model, GPCM, PCM
関連	4	5
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 Partial Credit Model is an extension of the Rasch measurement framework designed for ordered polytomous items — items whose responses fall into more than two ordered categories, such as partial-credit tasks in performance assessment or open-ended scoring rubrics. Proposed by Geoff Masters in 1982 and later generalised by Eiji Muraki in 1992, the model estimates a separate threshold (step) parameter for each adjacent-category transition within every item, allowing fine-grained calibration of how much each additional credit level contributes to locating a person on the latent trait.