His study investigated the correlational and gender-based analysis of item parameters of Geography qualifying examinations using Item Response Theory (IRT) in senior secondary schools in South-West, Nigeria. The study adopted an ex-post-facto research design, examining the responses of 1,200 Senior Secondary School II students who sat for the 2021 Geography Qualifying Examinations. A multistage sampling procedure was employed to select students’ responses to 50 multiple-choice Geography items from Ekiti State Qualifying Examination (ESQE) and Oyo State Qualifying Examination (OYQE), and 60 multiple-choice items from Ogun State Qualifying Examination (OGQE). The instruments were the adopted standardized qualifying examination question papers for 2021. Data were obtained from the respective State Ministries of Education through Optical Mark Reader (OMR) sheets. Responses were scored dichotomously, with correct options coded as 1 and incorrect options as 0. Item parameters of difficulty (b), discrimination (a), and guessing (c) under the One-Parameter Logistic (1PL), Two-Parameter Logistic (2PL), and Three-Parameter Logistic (3PL) models were estimated using BILOG-MG software. Hypotheses formulated were tested at 0.05 level of significance using Pearson Product-Moment Correlation Coefficient. Findings revealed that difficulty indices of Oyo and Ekiti States were significantly related, unlike Ogun State. A significant moderate linear relationship was observed between male and female difficulty parameters in Oyo State, while Ekiti and Ogun States exhibited low, non-significant relationships. Similarly, Pearson correlation for discrimination parameters was very low and non-significant across states; no significant linear relationship was found between male and female discrimination parameters in Oyo and Ekiti States, whereas Ogun State showed a low but significant relationship. It was therefore recommended that thorough item analysis should be institutionalized and given high priority by psychometric experts and test development specialists in Ministries of Education prior to final administration to ensure psychometric quality, fairness and gender invariance of test items.

Keywords: Item Response Theory, Geography examinations, Item analysis, Gender differences, Psychometric properties.