ERIC Number: ED390886
Record Type: Non-Journal
Publication Date: 1995-Jan
Reference Count: N/A
Detecting DIF for Polytomously Scored Items: An Adaptation of the SIBTEST Procedure. Research Report.
Chang, Hua-Hua; And Others
Recently, R. Shealy and W. Stout (1993) proposed a procedure for detecting differential item functioning (DIF) called SIBTEST. Current versions of SIBTEST can only be used for dichotomously scored items, but this paper presents an extension to handle polytomous items. The paper presents: (1) a discussion of an appropriate definition of DIF for polytomously scored items; (2) a modified SIBTEST procedure for detecting DIF for polytomously scored items; and (3) the results of two simulation studies comparing the modified SIBTEST with the Mantel-Haenszel and standardized mean difference procedures. One study used data constrained by the Rasch-like partial credit model, and the other used data with distinct discriminations across items. The simulations indicate that the methodology of including the studied item in matching subtests for controlling impact-induced Type I error tends to yield Type I and Type II error inflation rates that are highly unacceptable when the equal discrimination condition is violated. They provide evidence that the modified SIBTEST procedure is more robust with regard to controlling impact-induced Type I error rate inflation than the other procedures. (Contains 1 figure, 6 tables, and 26 references.) (Author/SLD)
Publication Type: Reports - Evaluative
Education Level: N/A
Sponsor: Office of Educational Research and Improvement (ED), Washington, DC.
Authoring Institution: Educational Testing Service, Princeton, NJ.