By partly randomizing item selection, a more evenly distributed exposure was obtained. The alphas-stratified method (CHANG; YING, 1999) also deals with underexposure. During the early stages of CAT, items are selected from strata with lower discrimination indices. These items are less informative, and tend to have low exposure rates. Limiting item selection to these strata increases the exposure rates of these items and reduces the problems of underexposure. The best results with exposure control problems have been obtained when methods for dealing with over exposure were combined with methods that deal with underexposure. Veldkamp, Verschoor e Eggen (2010) therefore proposed a method that combined both approaches.