Scale Comparability Between Nonaccommodated and Accommodated Forms of a Statewide High School Assessment

Abstract

Differential item/test functioning (DIF/DTF) are routine procedures to detect item/test unfairness as an explanation for group performance difference. However, unequal sample sizes and small sample sizes have an impact on the statistical power of the DIF/DTF detection procedures. Furthermore, DIF/DTF cannot be used for two test forms without common items. One of the advantages of person-fit analysis (PFA) is that even with small sample sizes, and/or no common items, PFA can still be utilized to investigate whether different subgroups are on the same scale. This study used simulation data and empirical data from a large-scale state high school assessment to demonstrate test fairness between nonaccommodated and accommodated forms. The results of this study showed that the accommodated form was comparable with the nonaccommodated form within the same construct, and PFA performs well for scale comparability purposes regardless of the size of the subgroups and number of common items.