Item Response Theory Detection of Items That Functioned Differentially in Philip Carter's Cognitive Ability Test Among Junior Secondary School Students in Ondo State, Nigeria

The study determined the test item that function differentially based on sex and school ownership and location among junior secondary students Ondo State These were with the view of ensuring the suitability of the use of Philip Carter’s Cognitive Abilities Test among secondary junior students in Ondo State. The study adopted survey design. The population for the study comprised all junior secondary school students in Ondo State and the study sample consisted of 1080 students. Philip Carter’s Cognitive Abilities Test was adopted for data collection. Data collected were subjected to Mantel-Haenszel DIF method of DIF assessment. The results showed that 14, 16 and 22 of the 30 items of the cognitive abilities test functioned differentially with respect to gender, school location and school type respectively. The study therefore concluded that some of the Philip Carter’s Cognitive Abilities Test items in its original format are not suitable for measuring Ondo State Junior Secondary school students’ cognitive ability. Keywords: Item Response Theory (IRT), Items that Functioned Differentially, Cognitive Ability Test