Effects of a Language Proficiency-Based Instructional Strategy on Academic Achievement of Private University STEM Students in Circular Measures in Oyo State, Nigeria

Abstract

STEM students at Nigerian private universities frequently struggle with circular measures, defaulting to rote memorisation of formulae rather than developing the conceptual understanding required for genuine problem-solving. This challenge is compounded by limited proficiency in English, the medium of instruction. The present study examined the effect of a language proficiency-based instructional strategy (LPS) on the academic achievement of private university STEM students in circular measures in Oyo State, Nigeria. A quasi-experimental pre-test/post-test design incorporated one experimental group and one control group from two private universities. Purposive and multistage sampling yielded 120 undergraduate 200-level STEM students (60 per institution). The Circular Measures Achievement Test (CMAT; 30 items; KR-20 = 0.87) served as the primary instrument. An a priori power analysis (Cohen’s f = 0.40, α = 0.05, power = 0.80) confirmed adequacy of the sample. Data were analysed using Analysis of Covariance (ANCOVA; df = 1, 117) with pre-test scores as the covariate. Results indicated a statistically significant main effect of the LPS on post-test achievement, F(1, 117) = 336.84, p < 0.001, η²p = 0.74. LPS students achieved a substantially higher adjusted mean (M = 25.37/30; 84.6%) compared with the conventional group (M = 18.37/30; 61.2%). The treatment effect was consistent across students with low, average, and high baseline English proficiency. Findings are interpreted through Vygotsky’s sociocultural theory, emphasising the Zone of Proximal Development and language as the primary scaffolding tool in technical learning. Recommendations are offered for classroom practice, teacher training, curriculum policy, and future research.