Equating test instruments using anchor to map student abilities through the R program analysis

This study aims at investigating the equivalence of mathematics try out scores of junior high school through anchor. In the study, the 2 Parameters Logistic (2PL) model of Item Response Theory (IRT) analysis was used through the Haebara method. The estimation step of the equating parameter utilized the equateIRT package in the R program. The results show that the relationship between try out questions of package 1 and package 2 cannot be said to be equivalent. After analyzing and calculating the regression equation, it can be concluded that package 2 of Mathematics National Examination (MNE) try out questions has a higher level of difficulty than package 1. Equating package 1 to package 2* through the Haebara method for the 2 PL model will provide equal or fair scores for the test takers who work on package 1 and package 2. The samples of questions were taken from MNE questions distributed in Makassar in 2014 which consisted of 2 question packages. Question package 1 was responded to by 2099 students, while question package 2 was responded to by 2068 students. The equating design used was a common item design. With the equating made, in the future, the test takers’ ability can be detected properly if they work on similar tests, even though test packages are relatively different