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Evaluation of Factors Affecting the Performance of the S-X2 Item-Fit Index
Journal article   Open access   Peer reviewed

Evaluation of Factors Affecting the Performance of the S-X2 Item-Fit Index

Hyung Jin Kim and Won-Chan Lee
Journal of educational measurement, Vol.59(1), pp.105-133
03/01/2022
DOI: 10.1111/jedm.12312
Appears in  UI Libraries Support Open Access
url
https://doi.org/10.1111/jedm.12312View
Published (Version of record) Open Access CC BY-NC-ND V4.0

Abstract

Orlando and Thissen (2000) introduced the S-X2 item-fit index for testing goodness-of-fit with dichotomous item response theory (IRT) models. This study considers and evaluates an alternative approach for computing S-X2 values and other factors associated with collapsing tables of observed and expected numbers (OE tables), which can affect flagging items. Results suggest that collapsing OE tables requires careful consideration of a trade-off between power and empirical type I error rate. Concurrent collapsing of score categories would be preferred over separate collapsing for its procedural simplicity, minimal effect of choice of a minimum cell value on empirical type I error rates, and reasonable type I error rates even for the most sparse condition in the study. For separate collapsing, a smaller minimum cell value is recommended as OE tables possess more sparseness (e.g., longer test lengths and smaller sample sizes) if inflated type I error rates are more of a concern in detecting items for misfit based on the S-X2 index. If it is more important to identify misfit items, the study results recommend using a larger minimum cell value for collapsing.
 Psychology Social Sciences Psychology, Applied Psychology, Educational Psychology, Mathematical UIOWA OA Agreement

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