COMPARISON OF PSYCHOMETRIC PROPERTIES OF WEST AFRICAN EXAMINATIONS COUNCIL AND NATIONAL EXAMINATIONS COUNCIL TEST ITEMS UNDER ITEM RESPONSE THEORY
The purpose of this study was to investigate the psychometric properties (reliability, validity, difficulty, discrimination, guessing and differential item function) of the items of the Biology examinations conducted by the National Examination Council (NECO) and the West African Examination Council (WAEC) using the Latent Trait Theory (IRT). This was against the backdrop of persistent public outcry that NECO questions were too cheap to pass. 14 Research questions and 7 hypotheses were formulated, tested, and analyzed. The sample was made up of 1800 senior secondary year three students from 36 secondary schools in the urban and rural areas of Benue State. The multistage stratified samplring technique was used. The NECO and WAEC Biology examination questions from 2000–2002 were the instruments for data collection. Maximum Likelihood estimation technique (using BILOG MG computer programme) was used to analyze the data in order to answer the research questions, according to IRT procedures. The t-test was used to analyse the data in order to test the hypotheses. It was found that the Biology examination items from the two examination bodies were equally reliable and valid. Biology items in the NECO – conducted examination were more difficult than those of WAEC of same years. Therefore, NECO questions were really not cheap to pass. WAEC items were more prone to guessing than those of NECO, and boys performed better in the WAEC items than in the NECO items. It was recommended that IRT procedures should be adopted by all examination bodies in Nigeria so that our measurement problems could be put to rest.