Psychometric Properties of Cognitive Development Test in Science using Rasch Model for Seventh Grade in Sultanate of Oman

Abstract

The study aimed to investigate the psychometric properties of the Cognitive Development Test in science subject for seventh grade using Rasch IRT model. The test contains 25 items with four choices. The test is administered to 8484 male and female students. The test was calibrated using Multilog 7.03 software to estimate item difficulty parameters, students’ ability parameters as well as test information function with Marginal Maximum Likelihood estimation method. Results supported the assumption for Rasch model and item fit for all test items. The marginal reliability with IRT was 0.83. The difficulty parameters ranged between 0.75 – 2.02 logit. Results also showed that the highest level of test information was at the average difficulty of the test which was close to the medium ability, whereas it was at minimal for low and high ability levels