Assessing Unidimensionality and Differential Item Functioning in Qualifying Examination for Senior Secondary School Students, Osun State, Nigeria

Abstract

This study assessed unidimensionality and occurrence of Differential Item Functioning (DIF) in Mathematics andEnglish Language items of Osun State Qualifying Examination. The study made use of secondary data. The resultsshowed that OSQ Mathematics (-0.094 ≤ r ≤ 0.236) and English Language items (-0.095 ≤ r ≤ 0.228) wereunidimensional. Also, there was occurrence of DIF items in both Mathematics and English Language multiple-choiceitems of the OSQE for 2008. Fourteen items representing 28% of the 50 items in the Mathematics examinationexhibited DIF and 10 items, representing 20% of the 50 items in the English Language examination exhibited DIF. Thestudy concluded that the Examination contained considerable number of items that exhibited DIF and thereforerequires adequate item quality improvement to justify its use as the inclusion or exclusion criterion of state candidate inWest African Examination Council.