Implementing problem-based learning on sound waves improves student learning outcomes

Problem-based learning (PBL) is widely recommended for physics topics that students find abstract, yet much of the supporting evidence comes from designs that cannot isolate what the model itself contributes. This study asked how far students’ cognitive achievement on sound-wave concepts changed across a PBL unit, and what a single-group design can legitimately establish about that change. A one-group pretest-posttest pre-experimental design was applied to one intact grade-11 class (n = 20) at an Indonesian Islamic senior secondary school. Achievement was measured with a ten-item test (five multiple-choice, five essay) administered before and after six 90-minute PBL sessions spread over three weeks. Scores rose from M = 58.25 (SD = 19.14) to M = 95.00 (SD = 6.28). The mean gain of 36.75 points was statistically significant, t(19) = 8.435, p < .001, dz = 1.89, 95% CI [27.63, 45.87], and the mean normalised gain was 0.88. The gain is large by any standard. It is also inflated: 11 of 20 posttest scores reached the ceiling of the test, which caps normalised gain at unity and compresses posttest variance. Absent a comparison group, the improvement cannot be attributed to PBL alone, and the estimate should be read as an upper bound.