Improving Cognitive Diagnostic Computerized Adaptive Testing by Balancing Attribute Coverage: The Modified Maximum Global Discrimination Index Method

Abstract

This article proposes a new item selection method, namely, the modified maximum global discrimination index (MMGDI) method, for cognitive diagnostic computerized adaptive testing (CD-CAT). The new method captures two aspects of the appeal of an item: (a) the amount of contribution it can make toward adequate coverage of every attribute and (b) the amount of contribution it can make toward recovering the latent cognitive profile. A simulation study shows that the new method ensures adequate coverage of every attribute, which improves the validity of the test scores, and defensibility of the proposed uses of the test. Furthermore, compared with the original global discrimination index method, the MMGDI method improves the recovery rate of each attribute and of the entire cognitive profile, especially the latter. Therefore, the new method improves both the validity and reliability of the test scores from a CD-CAT program.