Measuring change by means of a hybrid variant of the linear logistic model with relaxed assumptions

Abstract

The linear logistic model with relaxed assumptions (LLRA) was developed for measuring changes in qualitative data. It assumes item-specific person parameters and thus does not require homogeneous items to be presented to the persons at two points in time. The hybrid variant of this model maintains the multidimensionality of the person parameters, but it allows for different sets of items each of which is presented only once. In the model, a Rasch homogeneous item at2t with possibly differing difficulty corresponds to each item at t1. A short description of both models is followed by a first application of the hybrid LLRA to empirical data from a study on text comprehension. This example not only serves to demonstrate possible results when applying the LLRA, but is also used to outline the principle of hypothesis testing and model controls. Index terms: dichotomous data, linear logistic model, measuring change, Rasch model, text comprehension.