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	Polytomous Rasch Model	Ordinal Item Response Theory
Ämnesområde	Psykometri	Psykometri
Familj	Latent structure	Latent structure
Ursprungsår	1978–1982	1969
Upphovsperson	Gerhard N. Masters (Partial Credit Model); David Andrich (Rating Scale Model)	Fumiko Samejima (Graded Response Model, 1969); Gerhard Fischer & Georg Rasch lineage for partial credit
Typ	Item response model	Probabilistic latent trait model for ordered polytomous responses
Ursprungskälla	Masters, G. N. (1982). A Rasch model for partial credit scoring. Psychometrika, 47(2), 149–174.	Samejima, F. (1969). Estimation of latent ability using a response pattern of graded scores. Psychometrika Monograph Supplement, 34(4, Pt. 2), 1–97.
Alias	PRM, Rating Scale Model, Partial Credit Model, Polytomous IRT Rasch	polytomous IRT, ordinal IRT models, graded response models, ordinal latent trait models
Närliggande	6	6
Sammanfattning	The Polytomous Rasch Model extends the dichotomous Rasch framework to ordered response scales with three or more categories, such as Likert items or partial-credit tasks. It estimates person ability and item difficulty on the same interval-level logit scale, and it tests whether the response categories function as intended — prerequisites for rigorous ordinal measurement.	Ordinal item response theory (ordinal IRT) comprises a family of probabilistic models — most notably the Graded Response Model and the Partial Credit Model — that relate a respondent's standing on a latent trait to the probability of choosing each ordered response category on a polytomous item. It extends classical IRT beyond dichotomous items to the Likert-type and rating-scale items that dominate psychometric measurement.