<![CDATA[The ability to make evidence-based decisions is a critical competency for prospective science teachers to analyze problems, assess the quality of evidence, and consider uncertainties, and make decisions that take into account their merits and consequences. This study aims to examine the effectiveness of ontology–epistemology–axiology (OEA)-based philosophy of science instruction in improving evidence-based decision-making through a case study on saving electricity at home. The study employed a quantitative pre-experimental approach with a one-group pretest–posttest design. The research subjects were 31 fourth-semester students in the Science Education Program. The intervention was conducted over four sessions: OEA orientation and pretest; analysis of electricity consumption using OEA worksheets and the Claim–Evidence–Reasoning (CER) framework; evaluation of new evidence and decision revision; and a posttest accompanied by OEA reflection. The main instrument consisted of a case-based electricity conservation pretest–posttest package with five assessment dimensions: problem framing and stakeholders, energy calculations, evidence-based decision-making, identification of limitations and the need for additional data, and OEA reflection. The maximum rubric score of 20 was converted to a 0–100 scale. Data were analyzed using descriptive statistics, normality tests, paired-sample t-tests, N-gain, and Cohen’s d; LKM results and reflections were used as supporting data for the learning process. The results showed that the average score increased from 42.06 on the pretest to 90.90 on the posttest, with an N-gain of 0.84 in the high category. The difference in scores was significant (t = -44.03; p < 0.001) with a very large effect size (d = 7.90). Case-based OEA learning on energy conservation has the potential to strengthen students’ abilities to calculate and use quantitative evidence, revise decisions when evidence changes, and weigh trade-offs between cost savings and convenience.]]>
