Publication Date
4-2019
Document Type
Poster
Abstract
The S-χ2 item fit index is one of the few item fit indices that appears to maintain accurate Type I error rates. This study explored grouping examinees by the rest score or summed score, prior distributions for the item parameters, and the shape of the ability distribution. Type I error was slightly closer to the nominal level for the total-score S-χ2 for the longest tests, but power was higher for the rest-score S-χ2 in every condition where power was < 1. Prior distributions reduced the proportion of estimates with extreme standard errors but slightly inflated the Type I error rates in some conditions. When the ability distribution was not normally distributed, integrating over an empirically-estimated distribution yielded Type I error rates closer to the nominal value than integrating over a normal distribution.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Recommended Citation
DeMars, C. E. & Sauder, D. (2019, April). Considerations in S-χ2: Rest score or summed score, priors, and violations of normality. Electronic poster presented at the annual meeting of the National Council on Measurement in Education, Toronto, Canada.
Included in
Educational Assessment, Evaluation, and Research Commons, Quantitative Psychology Commons
