Predictive validity of the National Benchmark Test and National Senior Certificate for the academic success of first-year medical students at one South African university

BACKGROUND: South African medical schools use the results of the National Senior Certificate (NSC) examination for selecting students. Five of the nine medical schools also use the National Benchmark Test (NBT). The University of the Witwatersrand weights the NSC and NBT results equally in the selection process. This study addresses the predictive validity of the NBT and NSC for academic success. The association between the NBT proficiency levels and students’ progression outcomes was also investigated. METHODS: Data obtained from the University’s Business Intelligence Services for 1652 first-year medical students from 2011 to 2017 were analysed using hierarchical regression models and chi-square tests. The three NBT domains and four of the NSC subjects were the independent variables in the regression models, with the first-year grade point average for students who passed the first year as the dependant variable. The NBT performance levels and first-year progression outcome (passed, failed, or cancelled) were used in the chi-square analysis. Frequency tables were used to describe the cohort’s demographic details and NBT results. Crosstabs were used to analyse student performance according to the school quintile system. RESULTS: The three NBT domains explained 26% of the variance, which was statistically significant, R(2) = 0.263, F (3, 1232) = 146.78, p < 0.000. When the NSC subjects (Life Sciences, English, Mathematics, and Physical Science) were added to the regression equation, they accounted for an additional 19% of the variance, R(2) = 0.188, F (3, 1229) = 137.14, p < 0.000. All independent variables contributed 45% of the variance, R(2) = 0.451, F (6, 1229) = 166.29, p < 0.000. A strong association between the NBT proficiency levels and first-year students’ progression outcomes was observed. CONCLUSION: The NBT results, when weighted equally to the NSC results, explained more variance than the NSC alone in predicting academic success in the first year of the medical degree. The NBT should not only be used for selecting medical students but should also be used to place students with lower entry-level skills in appropriate foundation programmes and to identify students who are admitted to regular programmes who may need additional support.