<![CDATA[This research was motivated by the phenomenon of low mathematical concept mastery among junior high school students, particularly in statistics material. Conventional learning patterns, which tend to be monotonous and dominated by procedural formula delivery, result in students' difficulty in understanding the essence and interrelationships between concepts. This study aims to analyze the effectiveness of implementing the Contextual Teaching and Learning (CTL) approach integrated with PhET Interactive Simulation media in improving students' mathematical concept understanding. Utilizing a quantitative approach with a quasi-experimental design (The Nonequivalent Pretest–Posttest Control Group Design), this study involved a sample of 64 eighth-grade students at SMP Negeri 2 Langsa, divided into an experimental class (n = 32) and a control class (n = 32). Data were collected using an essay test assessing concept understanding that met the criteria for validity, reliability (r = 0.806), discriminating power, and difficulty index. The analysis results revealed a significant increase in the experimental class, with an average posttest score of 75.75 and an N-Gain index of 0.66, whereas the control class achieved an average posttest score of 64.84 with an N-Gain index of 0.51. Hypothesis testing via Independent Sample t-Test yielded a significance value (2-tailed) of p = 0.000 < 0.05. These findings demonstrate that implementing the contextual approach assisted by PhET Simulation is significantly more effective in facilitating mathematical concept understanding compared to conventional learning.]]>
