《《Item response theory and classical test theory an empirical comparison》.pdf

Educational and Psychological Measurem... June 1998 v58 n3 p357(25) Page 1 Item response theory and classical test theory: an empirical comparison of their item/person statistics. by Xitao Fan Despite theoretical differences between item response theory (IRT) and classical test theory (CTT), there is a lack of empirical knowledge about how, and to what extent, the IRT- and CTT-based item and person statistics behave differently. This study empirically examined the behaviors of the item and person statistics derived from these two measurement frameworks. The study focused on two issues: (a) What are the empirical relationships between IRT- and CTT-based item and person statistics? and (b) To what extent are the item statistics from IRT and those from CTT invariant across different participant samples? A large-scale statewide assessment database was used in the study. The findings indicate that the person and item statistics derived from the two measurement frameworks are quite comparable. The degree of invariance of item statistics across samples, usually considered as the theoretical superiority IRT models, also appeared to be similar for the two measurement frameworks. © COPYRIGHT 1998 Sage Publications, Inc. Classical test theory (CTT and item response theory (IRT) are widely perceived as representing two very different measurement frameworks. However, few studies have empirically examined the similarities and differences in the parameters estimated using the two frameworks. Prior to exploring this issue in some detail, some readers may appreciate a brief review of related theories. Additional detail is provided elsewhere (cf. Crocker Algina, 1986; McKinley Mills, 1989). Brief Review of CTT and IRT Although CTT has served the measurement community for most of this