Investigation of the Item Selection Methods in Variable-Length CD-CAT

Cognitive diagnostic computerized adaptive testing (CD-CAT) provides useful cognitive diagnostic information for assessment and evaluation. At present, there are only a limited numbers of previous studies investigating how to optimally assemble cognitive diagnostic tests. The cognitive discrimination index (CDI) and attribute-level discrimination index (ADI) are commonly used to select items for cognitive diagnostic tests. The CDI measures an item’s overall discrimination power, and the ADI measures an item’s discrimination power for a specific attribute. Su (Quantitative psychology research. Springer, Switzerland, pp. 41–53, 2018) integrated the constraint-weighted procedure with the posterior-weighted CDI and ADI for item selection in fixed-length CD-CAT, and found examinees yielded different precision. In reality, if the same precision of test results is required for all the examinees, some examinees need to take more items and some need to take fewer items than others do. To achieve the same precision for examinees, this study investigated the performance of the constraint-weighted procedure with the posterior-weighted CDI and ADI for item selection in variable-length CD-CAT through simulations.