01267nas a2200157   4500008003900000245009900039210006900138300001200207490000700219520076400226100001800990700001501008700001801023700002301041856004501064       2018                          d00aA Continuous a-Stratification Index for Item Exposure Control in Computerized Adaptive Testing0 aContinuous aStratification Index for Item Exposure Control in Co  a523-5370 v423 aThe method of a-stratification aims to reduce item overexposure in computerized adaptive testing, as items that are administered at very high rates may threaten the validity of test scores. In existing methods of a-stratification, the item bank is partitioned into a fixed number of nonoverlapping strata according to the items’a, or discrimination, parameters. This article introduces a continuous a-stratification index which incorporates exposure control into the item selection index itself and thus eliminates the need for fixed discrete strata. The new continuous a-stratification index is compared with existing stratification methods via simulation studies in terms of ability estimation bias, mean squared error, and control of item exposure rates.1 aHuebner, Alan1 aWang, Chun1 aDaly, Bridget1 aPinkelman, Colleen  uhttps://doi.org/10.1177/0146621618758289