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Title: A modified continuous a-stratification index for item exposure control in computerized adaptive testing Authors:  Ya-Hui Su - National Chung Cheng University (Taiwan) [presenting]
Abstract: Computerized adaptive testing (CAT) have been increasingly applied to many fields, including educational assessment, psychological testing, personnel recruitment, and clinical diagnosis. To ensure the validity of test scores, preventing items from being overexposed is very important to practical consideration because these items might be shared with current and future examinees. One popular method for item exposure control is a-stratification. When old or overexposed items would need to be removed from the item bank or new items would need be added into the item bank, the simulation studies would need to be conducted to determinate the optimal strata for a-stratification. It is undesirable for practitioners whenever the item bank is replenished frequently, such as high-stakes testing. Recently, a continuous a-stratification index (CAI) was proposed to incorporate item exposure control into the item selection index itself, and thus no need to partition the item bank into the fixed and discrete strata. However, the CAI still produced a high percentage of overexposed items that many practitioners couldn't view as negligible. Therefore, the study was to modify the CAI for limiting the maximum items exposure rate, and to investigate its efficiency with some current item exposure control methods for item selection in CAT.