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	Polytomous Differential Item Functioning (Polytomous DIF)	Model odpowiedzi stopniowanej (GRM)
Dziedzina	Psychometria	Psychometria
Rodzina	Latent structure	Latent structure
Rok powstania	1990s–2000s	1969
Twórca	Bruno D. Zumbo and colleagues (ordinal logistic regression framework); Robert D. Ankenmann, Hariharan Swaminathan and others (IRT-based extensions)	Fumiko Samejima
Typ	Measurement fairness / item bias detection	Item response theory / polytomous IRT model
Źródło pierwotne	Zumbo, B. D. (1999). A handbook on the theory and methods of differential item functioning (DIF): Logistic regression modeling as a unitary framework for binary and Likert-type (ordinal) item scores. Directorate of Human Resources Research and Evaluation, Department of National Defense.	Samejima, F. (1969). Estimation of Latent Ability Using a Response Pattern of Graded Scores. Psychometrika Monograph Supplement, No. 17.
Inne nazwy	Polytomous DIF, DIF for polytomous items, ordinal DIF analysis, graded-response DIF	Samejima's GRM, Derecelendirilmiş Tepki Modeli (GRM), graded IRT model
Pokrewne	4	7
Podsumowanie	Polytomous differential item functioning detects whether a test or survey item with more than two ordered response categories (e.g., Likert-type scales, partial-credit items) functions differently across groups such as gender, ethnicity, or language background, after controlling for the latent trait being measured. It extends classical binary DIF methods to ordinal response formats.	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.