手法を比較

	2母数ロジスティックIRTモデル（2PL）	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	1980	1969
提唱者	Frederic M. Lord	Fumiko Samejima
種類	Item response model / latent trait model	Item response theory / polytomous IRT model
原典	Lord, F. M. (1980). Applications of Item Response Theory to Practical Testing Problems. Erlbaum.	Samejima, F. (1969). Estimation of Latent Ability Using a Response Pattern of Graded Scores. Psychometrika Monograph Supplement, No. 17.
別名	two-parameter logistic model, 2PL model, 2PL IRT — İki Parametreli Madde Tepki Modeli	Samejima's GRM, Derecelendirilmiş Tepki Modeli (GRM), graded IRT model
関連	6	7
概要	The two-parameter logistic item response model, formalised by Frederic Lord (1980), describes the probability that a respondent answers a binary test item correctly as a smooth S-shaped function of the respondent's latent ability. By estimating a separate discrimination parameter for each item alongside a difficulty parameter, 2PL allows items to differ in how sharply they distinguish high- from low-ability respondents — making it the standard model for large-scale educational and psychological assessments.	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.