Sangbeak Ye

1. Introduction Local independence (LI) is a property that serves as a fundamental assumption underlying both parametric [1,2,3] and non-parametric [4,5,6] IRT models. Despite its importance, LI is easily violated in many situations (see, e.g., [7]). Model-wise, one can generally account for two main types of local dependence (LD), one related to misspecifications in the dimensionality of the model and one related to direct and invasive relations between the items in a test (see, e.g., [8]).