A multiple objective test assembly approach for exposure control problems in computerized adaptive testing

Over exposure and under exposure of items in the bank are serious problems in operational computerized adaptive testing (CAT) systems. These exposure problems might result in item compromise, or point at a waste of investments. The exposure control problem can be viewed as a test assembly problem with multiple objectives. Information in the test is maximized, item compromise is minimized, and pool usage in optimized. In this paper, a multiple objective method is developed to deal with both types of exposure problems. In this method, exposure control parameters based on observed exposure rates are implemented as weights for the information in the item selection procedure. The method does not need time consuming simulation studies, and it can be implemented conditional on ability level. The method is compared with Sympson Hetter method for exposure control, with the Progressive method and with alpha-stratified testing. The results show that the method is successful in dealing with both kinds of exposure problems, at the costs of an increased RMSE, while the bias remains comparable for all methods.