Investigating the Person Fit Statistics of Teenagers Participating in the Iranian University Entrance Exam Using the PerFit Package in R

The validity of the scores obtained from a test determines the accuracy and appropriateness of the inferences made about the examinee based on his test score. Person fit analysis offers several statistics that provide a basis for evaluating the conformity of the test score with a certain measurement model or with a group of examinees as an indicator of the validity of the test score. The PerFit package has been developed in R software for easy access to most of the person fit statistics. In this article, a review of person fit statistics is provided. With an example, it will be practically demonstrated how to use the main PerFit operators. Both numerical and graphic tools are described and shown using the biology scores of the applicants of the Iranian university entrance exam in 2022. The goal is to introduce the PerFit package as a powerful tool for measuring person fit and show how person fit statistics can be easily used for academic achievement tests.