Abstract:

The purpose of this study was to compare the equating errors of item and ability parameters obtained by performing scale transformation methods to two multidimensional test forms under various conditions. Sample size (1000-2000), common item ratio (20% and 40%), correlation between dimensions (0.1-0.5-0.9) and parameter estimation model (2PLM-3PLM) were taken as research conditions. Equating error (RMSE) was used to examine the accuracy of the scale transformation results. It was observed that the RMSE value generally decreased as the sample size and common item ratio increased and the correlation between dimensions decreased. Higher equating errors were obtained when the mean-sigma method was used. In the estimation of the discrimination parameter, lower RMSE values were obtained in 2PLM for all methods. In the estimation of difficulty and ability parameters, lower RMSE values were obtained in 2PLM for Stocking-Lord method and in 3PLM for mean-mean and mean-sigma methods.