Penelitian ini bertujuan untuk mengetahui pengaruh model pembelajaran Connecting, Organizing, Reflecting, dan Extending (CORE) terhadap kemampuan penalaran matematis siswa. Penelitian ini termasuk dalam jenis penelitian kuasi eksperimen dengan desain penelitan Posttest Only Control Group. Penelitian ini dilakukan di SMA Negeri 2 Tarakan dengan populasi penelitian adalah kelas XII MIPA tahun ajaran 2022/2023. Pengambilan sampel dilakukan dengan teknik simple random sampling dan diperoleh kelas XII MIPA 4 sebagai kelas eksperimen dan kelas XII MIPA 5 sebagai kelas kontrol. Pengumpulan data dalam penelitian ini menggunakan instrumen tes kemampuan penalaran matematis. Teknik analisis data yang digunakan adalah analisis deskriptif dan analisis inferensial. Analisis deskriptif meliputi rata-rata, skor per indikator, dan standar deviasi. Sedangkan analisis inferensial terdiri dari uji regresi linear sederhana dan uji t (independent sample t-test). Hasil penelitian menunjukkan nilai rata-rata posttest kelas eksperimen lebih baik daripada kelas kontrol yaitu 76,47 untuk kelas eksperimen dan 49,89 untuk kelas kontrol dalam skala nilai 100. Berdasarkan hasil uji regresi linear sederhana diperoleh persamaan Y ̂=49,889+26,582D, dimana pada kelas kontrol variabel dummy (D) bernilai 0 karena tidak menerima perlakuan, maka nilai rata-rata kemampuan penalaran matematis siswa pada kelas kontrol adalah sebesar 49,889+26,582(0)=49,889. Sedangkan pada kelas eksperimen variabel dummy (D) bernilai 1 karena menerima perlakuan, maka nilai rata-rata kemampuan penalaran matematis siswa pada kelas eksperimen adalah sebesar 49,889+26,582(1)=76,471. Hal ini berarti terdapat pengaruh dari model pembelajaran CORE terhadap kemampuan penalaran matematis. Selain itu, hasil uji t diperoleh nilai t_hitung lebih besar dari t_tabel (t_hitung=15,135 > t_tabel=1,998) yang artinya terdapat pengaruh yang signifikan dari model pembelajaran CORE terhadap kemampuan penalaran matematis siswa. Pengaruh yang diberikan ini adalah sebesar 78,2% dan sisanya 21,8% dipengaruhi oleh di luar variabel penelitian.

Kata Kunci: CORE, Penalaran Matematis

This research aimed to determine the effect of Connecting, Organizing, Reflecting, and Extending (CORE) learning model on students' mathematical reasoning ability. This research was a type og quasi-experimental research with a Posttest Only Control Group Design. This research was conducted at SMA Negeri 2 Tarakan with class XII MIPA in the 2022/2023 academic year as the population. The sample was chosen by using a simple random sampling technique and obtained class XII MIPA 4 as the experimental group and class XII MIPA 5 as the control one. The data ere collected using a mathematical reasoning ability test and were then analyzed using descriptive and inferential analysis. The descriptive analysis contained mean score, score per indicator, and standart deviation, while the inferential analysis comprised of simple linear regression test and t-test (independent sample t-test). The results showed that the mean score of the posttest of the experimental class was better than that of the control class, namely 76.47 for the experimental class and 49.89 for the control class on a scale of 100. Based on the result of a simple linear regression test, it was obtained the equation Y ̂=49.889+26.582D, in which the dummy variable (D) in the control class was 0 because it did not received any treatment. The mean score of students' mathematical reasoning ability in the control class was 49.889+26.582(0)=49.889. Whereas the dummy variable (D) in the experimental class was worth 1 because it received treatment, then the mean score of students' mathematical reasoning ability in the experimental class was 49.889+26.582(1)=76.471. This meant that there was an effect of the CORE learning model on mathematical reasoning ability. In addition, the result of the t-test obtained that the value of the t_count was greater than the t_table (t_count=15.135 > t_table=1.998) which indicated that there was a significant effect of the CORE learning model on students' mathematical reasoning ability. The effect yielded was 78.2% and the remaining 21.8% was influenced by other research variables. Keywords: CORE, Mathematical Reasoning