Methoden vergleichen

	Polytomes Rasch-Modell	Item Response Theory (IRT)
Fachgebiet	Psychometrie	Psychometrie
Familie	Latent structure	Latent structure
Entstehungsjahr	1978–1982	1952–1968
Urheber	Gerhard N. Masters (Partial Credit Model); David Andrich (Rating Scale Model)	Frederic M. Lord (and Allan Birnbaum for the 2PL/3PL models)
Typ	Item response model	Probabilistic measurement model
Wegweisende Quelle	Masters, G. N. (1982). A Rasch model for partial credit scoring. Psychometrika, 47(2), 149–174.	Lord, F. M. & Novick, M. R. (1968). Statistical Theories of Mental Test Scores. Addison-Wesley.
Aliasnamen	PRM, Rating Scale Model, Partial Credit Model, Polytomous IRT Rasch	IRT, latent trait theory, item characteristic curve theory, modern test theory
Verwandt	6	5
Zusammenfassung	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.	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.