The Model Selection Methods About The Model With The Testlet Effect

This paper emphasizes on the study of the model with the testlet effect and its application in practice. It draws lessons from the CVLL criterion which is better than the other criterions and Gibbs sample which is applied generally. We will select the better model from the prepared models to describe the character of data by analyzing practice.As known, the purpose of theory is to be applied in practice and direct practice. For this reason, we study the model with the testlet effect. First, we select three models which are more reasonable for the mathematic test of the second tests whose objects are civil students in junior high school in 1993 in Taiwan by reading literature and testing again and again: the model with the testlet of one parameter logistic(model 1), the model with the testlet of two parameters logistic(model 2), and general model. Second, we estimate parameters with the aid of the Gibbs sample. Last, we select a better model with the aid of the model selection methods CVLL criterion.The conclusion is that model 2 is most suitable for the test, the model 1 is second and the model 3 is last. whereas the (a|^)_j1 and (a|^)_j2 in the general model is close to equal, it is effective to prove the model 2 have described the character of data correctly in fact. Analyze from the test itself, we know the influence of the testlet effect is not great, so that the variance of model 2 and general model are small is very reasonable.