Abstract: Testlets-composed tests are commonly used in education and psychology fields, but items in the same testlet may violate the assumption of local item independence and lead to local item dependency (LID). Thus, in order to increase parameter estimation accuracy, probing into methods of handling LID is of significant importance. In this paper, the authors summarize and assess four methods in processing LID, including standard IRT model, polytomous IRT model, testlet response model and bi-factor model. Taking parameter estimation accuracy as the criterion, the authors further summarize the effects and suitable conditions of each method and provided corresponding comments. This paper will provide reference for method selection when processing LID. Future research directions are discussed as well.

Key words: testlet, IRT model, local item dependency (LID)