Abstract
Differential Item Functioning poses a threat to test fairness and validity in
educational assessments. To this end, this study probes the incidence of DIF in the Senior
School Certificate Agricultural Science Examination (SSCASE) across school locations in
Southwestern Nigeria. It determined the magnitude of DIF using item parameters in SSCASE.
The study applies one, two and three-parameter logistic models to analyze the dichotomous
data responses of 818 randomly selected students from urban and rural locations. The expost
facto design adopted the 2015 National Examination Council SSCE in Agricultural
Science as its instrument (α =0.887) in this study. The study population comprised SSCE
candidates from Osun, Ondo, and Oyo. The results showed the magnitude of DIF in SSCASE
was large and moderate (1PLM=0.52 significant DIF, 2PLM=0.45 moderate DIF, 3PLM=0.47
moderate DIF) across school locations. The study concluded that 1, 2 and 3 PLMs can
produce fair items in SSCASE.