Verification of Differential Item Functioning (DIF) Status of West African Senior School Certificate Examination (Wassce) in Chemistry
This study investigated test item bias and Differential Item Functioning (DIF) of West African Senior School Certificate Examination (WASSCE) in chemistry. The major objective was to examine how WASSCE items in chemistry function differentially with respect to gender and location. In Aba education zone of Abia, 50 secondary schools were purposively selected, stratified by gender and location. A total of 675 SS III students were selected. The Chemistry Achievement Test had 50 items. Maximum Likelihood Estimation in the BILOG MG Computer programme was used to answer the two research questions. The result indicated that out of the 50 items, 16% showed moderate evidence of DIF by gender. For location, DIF was detected for 46% of the items. Therefore, chemistry items in WASSCE have a fairly substantial degree of DIF especially with respect to location. It was recommended that DIF analysis be applied in test development to use less biased items.