Abstract

The study evaluated the Rasch Model in determining the reliability and difficulty indices of senior secondary school mathematics tests in Rivers State. With the instrumentation design, the study specifically examined person reliability, item reliability and the difficulty level of the items. Three research questions and associated null hypotheses guided the study. From a population of 199,602 students in the public senior secondary schools in Rivers State in the 2025/2026 academic session, a sample of 480 Senior Secondary Two (SS2) students was selected for the study through a multi-stage sampling procedure. “Mathematics Performance Test (MPT) for SS2 Students” was the instrument used for data collection. The MPT was validated by Mathematics and Evaluation experts. The KR₂₀ was used to establish the internal consistency reliability of the instrument, and a reliability coefficient of 0.76 was obtained. Data was analysed using the Rasch model with the aid of the eRm package in R software. Results of the study showed that the senior secondary school mathematics tests in Rivers State possessed high person reliability, good item reliability, and provided a reasonably varied range of item difficulties. It was recommended that mathematics test developers should utilise the Rasch model for calibration of mathematics test items to ensure that all the items attain high reliability coefficients to dependably measure the students’ mathematics abilities, and that mathematics teachers should adopt mathematics tests that contain a varied range of easy, moderate and difficult items to create a level playing field for both low and high scorers.