Trends in the Psychometric Characteristics of NECO Mathematics Senior School Certificate Examination Over a Period of Five Years (2020-2024) among Osun State’s Candidates

The study examined the psychometric characteristics of the NECO SSCE Mathematics test in Osun State, Nigeria, spanning from 2020 to 2024. A random sample comprising 10% of the total of 211,753 candidates was selected for the study. The examination item responses were used to examine three factors: item difficulty, item discrimination, and test reliability. The researchers used descriptive statistics, one-way ANOVA, and Scheffe post hoc tests to analyse the collected data. The results showed that item difficulty remained largely stable over the years, except in the most recent examination year, which exhibited a marked change. The five-year period showed major changes in item discrimination indices because item quality testing yielded different results, whereas overall item discrimination remained within acceptable limits. The KR-20 reliability coefficients were high throughout the study, indicating that the test maintained consistent internal consistency during the assessment. The study found that the NECO SSCE Mathematics examination is highly reliable but requires ongoing psychometric assessment to maintain standards across periods, including reliability, fairness, and validity.