Performance of the Generalized S-X[Superscript 2] Item Fit Index for Polytomous IRT Models

Orlando and Thissen's S-X[superscript 2] item fit index has performed better than traditional item fit statistics such as Yen' s Q[subscript 1] and McKinley and Mill' s G[superscript 2] for dichotomous item response theory (IRT) models. This study extends the utility of S-X[superscrip...

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Bibliographic Details
Published in:Journal of educational measurement 2008-12, Vol.45 (4), p.391
Main Authors: Kang, Taehoon, Chen, Troy T
Format: Article
Language:English
Subjects:
Educational Testing
Generalization
Item Response Theory
Psychological Testing
Rating Scales
Online Access:Get full text
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Summary:Orlando and Thissen's S-X[superscript 2] item fit index has performed better than traditional item fit statistics such as Yen' s Q[subscript 1] and McKinley and Mill' s G[superscript 2] for dichotomous item response theory (IRT) models. This study extends the utility of S-X[superscript 2] to polytomous IRT models, including the generalized partial credit model, partial credit model, and rating scale model. The performance of the generalized S-X[superscript 2] in assessing item model fit was studied in terms of empirical Type I error rates and power and compared to G[superscript 2]. The results suggest that the generalized S-X[superscript 2] is promising for polytomous items in educational and psychological testing programs. (Contains 2 figures, 3 tables, and 52 formulas.)
ISSN:0022-0655
DOI:10.1111/j.1745-3984.2008.00071.x