The Improvement of Mathematical Communication Skill Through Project Based Learning with STEM Strategy

---This study was conducted to determine the influence of Project Based Learning (PjBL) with science, technology, engineering, and mathematics (STEM) to improve students’ mathematical communication skill (MCS) of seventh grade students in junior high school. This study was a quantitative research design. Population of this study were seventh grade students of SMP Negeri 12 Semarang and area random sampling used as a sampling technique selection.. The research subject were 32 students of Grade VII-G as experimental group which using PJBL with STEM strategy and 32 students of Grade VII-H as control group which using Discovery Learning model. Data was then analyzed using independent t-test, paired t-test and N-Gain test. The result of this study showed that learning process using PjBL with STEM strategy way more effective to improve MCS of the students which obtained that N-Gain diagrams by 0.703 in the high category, although there was not significant difference mean result both experiment and control group toward MCS. This PjBL with STEM strategy can be used in Indonesian learning process as well as for learning models that train MCS of the students especially for outdoor learning and 21 st Century skill.