Recent research has shown that over-extraction of latent classes can be observed in the Bayesian estimation of the mixed Rasch model when the distribution of ability is non-normal. This study examined the effect of non-normal ability distributions on the number of latent classes in the mixed Rasch model when estimated with maximum likelihood…

The purpose of this study was to explore what may be contributing to differences in performance in mathematics on the Trends in International Mathematics and Science Study 2007. This was done by using a mixture item response theory modeling approach to first detect latent classes in the data and then to examine differences in performance on items…

Studies of international mathematics achievement such as the Trends in Mathematics and Science Study (TIMSS) have employed classical test theory and item response theory to rank individuals within a latent ability continuum. Although these approaches have provided insights into comparisons between countries, they have yet to examine how specific…