Performance of the Generalized S-X2 Item Fit Index for Polytomous IRT Models

Orlando and Thissen's S-X² item fit index has performed better than traditional item fit statistics such as Yen's Q₁ and McKinley and Mill's G² for dichotomous item response theory (IRT) models. This study extends the utility of S-X² to polytomous IRT models, including the generalized...

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Bibliographic Details
Published inJournal of educational measurement Vol. 45; no. 4; pp. 391 - 406
Main Authors Kang, Taehoon, Chen, Troy T.
Format Journal Article
LanguageEnglish
Published Malden, USA Blackwell Publishing Inc 01.12.2008
Wiley Subscription Services
Subjects
Applied psychology
Calibration
Computer software
Credit
Datasets
Education
Item response theory
Measurement
Modeling
Parametric models
Power
Sample size
Simulations
Test scores
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Summary:Orlando and Thissen's S-X² item fit index has performed better than traditional item fit statistics such as Yen's Q₁ and McKinley and Mill's G² for dichotomous item response theory (IRT) models. This study extends the utility of S-X² to polytomous IRT models, including the generalized partial credit model, partial credit model, and rating scale model. The performance of the generalized S-X² in assessing item model fit was studied in terms of empirical Type I error rates and power and compared to G². The results suggest that the generalized S-X² is promising for polytomous items in educational and psychological testing programs.
Bibliography:ark:/67375/WNG-WTJG6DR9-X
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ArticleID:JEDM071
ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 23
ISSN:0022-0655
1745-3984
DOI:10.1111/j.1745-3984.2008.00071.x