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Performance of the Generalized S‐X 2 Item Fit Index for Polytomous IRT Models
Author(s) -
Kang Taehoon,
Chen Troy T.
Publication year - 2008
Publication title -
journal of educational measurement
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.917
H-Index - 47
eISSN - 1745-3984
pISSN - 0022-0655
DOI - 10.1111/j.1745-3984.2008.00071.x
Subject(s) - polytomous rasch model , item response theory , index (typography) , econometrics , statistics , psychology , rating scale , type i and type ii errors , mathematics , psychometrics , computer science , world wide web
Orlando and Thissen's S‐X2item fit index has performed better than traditional item fit statistics such as Yen's Q 1 and McKinley and Mill's G 2 for dichotomous item response theory (IRT) models. This study extends the utility of S‐X2to polytomous IRT models, including the generalized partial credit model, partial credit model, and rating scale model. The performance of the generalized S‐X2in assessing item model fit was studied in terms of empirical Type I error rates and power and compared to G 2 . The results suggest that the generalized S‐X2is promising for polytomous items in educational and psychological testing programs.