An Examination of Item Response Theory Item Fit Indices for the Graded Response Model

In: Organizational research methods: ORM, Volume 14, Issue 1, p. 10-23

Abstract

The current study examined the Type I error rates and power of several item response theory (IRT) item fit indices used in conjunction with the graded response model (GRM). Specifically, S — χ2, χ2*, and adjusted χ 2 degrees of freedom ratios (χ2/dfs) were examined. Model misfit was introduced by manipulating item parameters and by using a different IRT model to generate item data. Results indicated lower than expected Type I error rates for S — χ2 and χ 2*. Adjusted χ2/dfs resulted in large Type I error rates when used with cross validation and very low Type I error rates when used without cross validation. χ2* and adjusted χ 2/dfs without cross validation were the most powerful overall.