Selection the best method of equating using Anchor-test design in Item Response Theory case study: Ph.D test

The goal of this research is finding the best method of equating data in item response theory. For that purpose, we are using the data of Ph.D test in  Statistic major for two consecutive years 92 and 93. For analyzing, we are specificly using the tests of Statistics major which includes 45 questions. Parameters of test and ability of individuals are considered according to the three parametrs model and by using the MULTILOG software. In this study, we are using the Mean-Mean method, Mean-Sigma, Haebara, and Stocking-Lord methods by considering the unequal groups with Anchor-test design, and we are using the root mean square error for choosing the optimal solution. The results of this study show that the methods under characteristic curve are more accurate.