Comparison Study Of Item Selection Strategies Of Computerized Adaptive Testing With The Samejima Graded Response Model

This paper investigates the comparison research between six item selection strategies of CAT, based on the Samejima Graded Response Model from such four perspectives as accuracy of ability estimations, stability of item selection strategy, efficiency of testing and whether the item bank are evenly selected. The simulation method and five evaluation indices are adopted. The results show that:1) under the condition that the difficulty parameters follow the normal distribution, the strategy of the difficulty orders matching with the ability, is slightly better than that of the mean of the difficulty orders matching with ability. The item selection strategy of the item maximum information is more efficient than that of the ability maximum information, while the items are worse evenly selected. A_stratified selection strategy of the medium is slightly better than that of the mean.2) when the item difficulty parameters follow the even distribution, in the aspect of whether the items are evenly selected, the strategy of the medium of the difficulty orders matching with ability is slightly worse than that of the mean matching with ability, while on other perspectives that are mentioned above, the former is slightly better than the later., but As far as the A_stratified selection strategy is concerned, it is another case, the medium strategy is better than the mean strategy in the aspect whether the items are evenly selected, and on other perspective, it is slightly worse, in the aspects of accuracy of ability estimation and efficiency, item selection strategy of ability maximum information is better than that of the item maximum information, while it is worse in the aspect of whether the items are evenly selected.3) in general, under the conditions that the item difficulty parameters follow different distributions, A_stratified selection strategy is slightly better than other strategies. As far as the A_stratified selection strategy itself is concerned, in every stage, the strategy of the medium of difficulty orders matching with ability is better than that of the mean matching with ability.4) the constructs of the item parameters have effect on the results of CAT item selection strategies.