Assessment of 2PL, 3PL and 4PL Model-Fit on the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-IV) Using Item Response Theory

The purpose of this paper is to investigate into which of the models of item Response Theory that fits into the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-IV) with a view to adapting the WPPSI-IV to measure the intelligence of Nigerian children aged approximately 7. The design of the study was survey which allows for data to be collected through the administration of the WPPSI-IV to 387 pupils. Data collected was analysed with the use of factor analysis on 2PL, 3PL and 4PL models of item Response Theory. Findings from the study indicate that 2PL model was more fit for WPPSI-IV than 3PL and 4PL models. It was recommended that the WPPSI-IV should be adapted or adopted by schools to measure pupils intelligence approximately aged 7 because the instrument is moderately difficult and discriminated moderately among the testees and that schools should be well furnished with audio-visual materials to promote critical thinking of children or pupils, this will go a long way in making them to do well in intelligence tests.