Assessing differential item functioning in core educational courses: Implications for gender and lecturer experience in Ghanaian higher education

Abstract

This study examines the Differential Item Functioning (DIF) of examination papers in core educational courses offered by undergraduates in a public university in Ghana, focusing on gender and lecturing experience and their implications for assessment standards. A The study is underpinned by the measurement invariance theory that posits that test items should measure the same construct across different groups in the same way. Cross-sectional research design was employed, with 872 students sampled out of 5221 across six departments. Item analysis and DIF evaluation were conducted using descriptive statistics, factor analysis, and item response theory (IRT) models. Results revealed variability in item difficulty, discrimination, and response patterns, with 40% of items classified as moderately difficult and 20% as very difficult. Item discrimination was generally robust, though a few items displayed poor discrimination, necessitating revision. The analysis revealed no statistically significant difference in differential item functioning (DIF) scores between male and female students. Male students had a mean DIF score of 115.03 (SD = 263.41), while female students had a mean DIF score of 113.67 (SD = 259.14). The t-test results, t(866) = 0.072, p = 0.943, indicate that the observed differences were not statistically significant. However, lecturer experience was found to have a significant impact on students' DIF scores. Students taught by experienced lecturers had a mean score of 149.56 (SD = 353.80), compared to a mean score of 74.02 (SD = 4.66) for those taught by inexperienced lecturers. The t-test results, t(465.19) = 4.61, p < 0.000, confirmed a statistically significant difference, with a mean difference of 75.54 and a 95% confidence interval ranging from 40.99 to 110.09. These findings suggest that lecturer experience plays a crucial role in influencing DIF scores. These findings underscore the importance of aligning test items with instructional objectives, enhancing lecturer training, and refining test designs to mitigate biases. It is recommended that the university should implement routine DIF analyses to proactively identify and rectify biased test items. This practice will help maintain fairness and equity in educational assessments across different demographic groups. Given the significant impact of lecturer experience on student performance, the institution should invest in continuous professional development programmes for faculty. Training should focus on effective teaching strategies, assessment design, and student engagement. The study contributes to the literature on test fairness and equity in higher education, emphasizing the need for ongoing assessment improvements and expanded research to address limitations related to sample diversity and contextual generalizability.