This study investigates the impact of violating the local item independence assumption by loading certain items onto a second dimension on test equating errors in unidimensional and dichotomous tests. The research was designed as a simulation study, using data generated based on the PISA 2018 mathematics exam. Analyses were conducted under 36…

Mixture Rasch (MixRasch) models conventionally assume normal distributions for latent ability. Previous research has shown that the assumption of normality is often unmet in educational and psychological measurement. When normality is assumed, asymmetry in the actual latent ability distribution has been shown to result in extraction of spurious…