Assessing the differential item functioning of 2018 WASSCE mathematics achievement tests in Lagos State, Nigeria

Abstract

This study explored the Differential Item Functioning (DIF) of 2018 West Africa Examination Council's Mathematics Objectives Tests Items in Lagos, Nigeria. The research design used for the investigation is a descriptive survey design. The population included all Senior Secondary Three (SS3) students who enrolled for the 2020 West Africa Senior Secondary Certificate Examination (WASSCE) in Lagos State. Multistage sampling procedure was used to select 1334 students from eighteen secondary schools (three schools from each educational district). Three research questions guided the study. The research questions were subjected to item differential functioning analysis using BILOG MG model. Results demonstrated that six items out of the 50 items function differentially in regard to gender. The results also showed that 15 items out of the 50 items work differentially in regard to location, while all the 50 items function differentially with regard to school ownership. The study uncovered that item analysis using item response theory approach isn't adequate to pass judgment on the nature the test, it is necessary that the item bias is also estimated. It was thus recommended that examination bodies and test developers should include item bias during item analysis.