The Research On Selecting Items And Controlling Exposure Rate Of Computerized Adaptive Testing With Cognitive Diagnostic

With the popularity of computer and the attention of people paying to education,the traditional test only provides a total score for examinees, which far can’t satisfypeople’s needs. At the same time, Item Response Theory (IRT) is rapidly developing.Thus produce Computerized Adaptive Testing (CAT), which not only provides the testscore, but also can estimate the ability level of examinees.Early CAT is basically based on IRT, as IRT-CAT. Although IRT-CAT canestimate examinees’ ability level, can’t provide detailed information of the diagnosisfor examinees. In other words, which knowledge the examinee masters and which theexaminee couldn’t master. That is that there is no way to take remedial measure forthe examinees. Along the cognitive psychology combines with the psychometric,Computerized Adaptive Testing with Cognitive Diagnosis (CD-CAT) is produced.CD-CAT not only provides a test score for examinees, but also provides detaileddiagnostic information for examinees. In other words, which knowledge the examineemasters and which the examinee couldn’t master. That is getting the examinee’s innerknowledge states and cognitive skills, then teachers guide his/her study, which helpsguide teachers’ teaching and students’ learning.CD-CAT like IRT-CAT, the most importance is the item selection strategy. Thispaper compares the diagnostic accuracy of three item selection strategies in the bankwith or without including the reachability matrix based on four attribute hierarchystructure. The three selection strategies are Modified Global Discrimination IndexMethod (MGDI), CDM Information Index (CDI) and a new method MGCDIcombining MGDI with CDI. This paper adopts the method of fixed the itemparameters based on the DINA model, in order to eliminate the influence of the itemparameters. Select the items from the reachability matrix as starting point, willinevitably lead to the exposure rate of the items from the reachability matrix is high,and the security of the item bank is threatened. In this paper, MPI is used in theselection strategies to control the exposure rate of the items and the use of the itembank is more uniform. The results of Monte Carlo simulation show that the new wayselects the items from the reachability matrix as starting point, and then other items from the bank including the reachability matrix with maximizing MGCDI, MGDI orCDI, the diagnostic accuracy of which is higher than selecting all items from the bankwithout including the reachability matrix with maximizing MGCDI, MGDI or CDI.The selection strategies of using MPI can effectively control the exposure rate.