Problem-Based Learning and Final Cooling-System Competency in Heavy-Duty Diesel Engine Education: A Quasi-Experimental Pretest-Posttest Study

Abstract

Problem-Based Learning (PBL) is suited to technical education because it organizes learning around authentic problems and diagnostic reasoning. This study examined whether PBL was associated with higher final cooling-system competency in heavy-duty diesel engine learning and whether any advantage reflected larger learning gain or higher endpoint attainment. A quasi-experimental pretest-posttest design involved 61 Grade XI Heavy Equipment Engineering students (PBL, n = 32; control, n = 29). Descriptive statistics, paired tests, Welch comparisons, normalized gain, effect sizes, non-parametric sensitivity analyses, and ANCOVA with HC3 robust standard errors were applied. Both groups improved substantially (PBL: 50.00 ± 9.84 to 89.06 ± 6.02; control: 45.69 ± 8.53 to 84.83 ± 8.40; both p < 0.001), while raw gains were virtually identical (39.06 vs. 39.14; p = 0.979). The PBL group nevertheless achieved a higher post-test score (difference = 4.23 points, 95% CI 0.44–8.03; Hedges’ g = 0.58), and the baseline-adjusted difference remained 3.98 points (HC3 p = 0.048). PBL was therefore associated with higher final attainment, not a larger absolute gain. Evaluating vocational pedagogy through both change and endpoint performance provides a more precise interpretation of instructional effects in intact-class designs.