مرکز منطقه ای اطلاع رساني علوم و فناوري - Comparison of IRT Equating Methods Using the Common-Item Nonequivalent Groups Design

Abstract :

The purpose of this research was to equate the test for which were constructed in different conditions through scaling methods based on item response theory and to compare the results obtained from these methods. The research was conducted with using dichotomous simulated data which was consistent with two and three parameter logistic model. In order to equate two test forms “the common-item nonequivalent groups” was used in this research. WINGEN3 program was utilized for data generation and 50 replication were done for 36 different condition used in this research. PARSCALE 4.1 was utilized for the prediction of item parameters and IRTEQ was utilized for test equating and scaling in separate calibration. The results obtained from this simulation study were evaluated based on equating error (RMSE) criterions. The results revealed that, when the conditions evaluated generally, the best equating occurred in 3000-subjects samples, 80-item tests, groups have similar ability distribution, using and mean-mean methods. Moreover, the results indicated that methods had less equating errors when large sample sizes together with long tests were used in groups which had similar ability distributions under the conditions considered in this research.