<![CDATA[This study aims to determine the effectiveness of the cooperative learning model Student Teams Achievement Division (STAD) on the mathematics learning outcomes of eighth-grade students at SMP Negeri 1 Halongonan. The background of this research is the low mathematics learning outcomes of students, which are caused by a lack of conceptual understanding, low learning motivation, and the perception that mathematics is a difficult subject. This research employed an experimental method with a One Group Pretest-Posttest Design. The research subjects consisted of 18 eighth-grade students at SMP Negeri 1 Halongonan. The research instruments included a learning outcome test and an observation sheet for learning activities. Data were analyzed using normality, homogeneity, and t-tests with the aid of SPSS version 27. The normality test results indicated that the data were normally distributed, with significance values of 0.200 > 0.05 for the pretest and 0.174 > 0.05 for the posttest. The homogeneity test showed a significance value of 0.149 > 0.05, indicating that the data were homogeneous. The average student learning outcome before applying the STAD model (pretest) was 49.83, while after its application (posttest), it increased to 83.39. The t-test results showed a significance value of 0.000 < 0.05, meaning that H₀ was rejected and Hₐ was accepted. This indicates a significant difference between students’ learning outcomes before and after implementing the STAD model. The correlation value between the two variables was 0.248, showing a positive relationship between the implementation of the STAD model and the improvement of students’ mathematics learning outcomes. Based on these results, it can be concluded that the cooperative learning model of the STAD type is effective in improving the mathematics learning outcomes of eighth-grade students at SMP Negeri 1 Halongonan.]]>
