Equating of standardized science subjects tests using various methods: which is the most profitable?

A good test set can be reflected in the quality of the items. It can measure the ability of the test takers reasonably even though they are distributed in several question packages. This study uses an exploratory, descriptive method to determine the equivalence of standardized test sets in science subjects for junior high schools in Indonesia. The data were obtained from the database of Junior High School National Examination results in the subject of Natural Sciences, which consisted of 5 question packages with 40 items/package. The equating technique uses the Item Response Theory 3 PL approach with the help of R Studio Software. The research results show that the national exam questions, which consist of 5 question packages, have a good level of item difficulty and all guesses. However, the discrimination index and several items obtained unfavorable results. In addition to the results of equating the graphical method using the closeness of the test characteristic curve, the Stocking & Lord methods produce the most equivalent scores. These findings can be a reference for test developers or researchers in the field of measurement to produce better and more accurate test kits.