Penelitian ini dilatarbelakangi oleh rendahnya kemampuan berpikir kritis siswa pada pelajaran mata pelajaran Ilmu Pengetahuan Alam dan Sosial (IPAS). Tujuan dari penelitian ini untuk mendeskripsikan pengaruh model pembelajaran Research based learning (RBL) terhadap kemampuan berpikir kritis siswa dan Peningkatan (Gain) terhadap kemampuan berpikir kritis siswa dengan menggunakan model pembelajaran Research based learning (RBL). Subjek penelitian sebanyak 50 siswa. Pendekatan penelitian yang dilakukan dalam penelitian ini yaitu pendekatan kuantitatif dengan metode eksperimen yaitu quasi eksperimen dengan desain penelitiannya yaitu nonequivalent control group design. Pengumpulan data dilakukan dengan menggunakan instrumen tes berupa soal uraian pretest-postest untuk mengukur kemampuan berpikir kritis siswa terhadap penerapan model pembelajaran Research based learning (RBL). Berdasarkan analisis data nilai rata-rata sesudah diberikan perlakuan (postest) lebih besar dari nilai rata-rata sebelum diberikan perlakuan (pretest). Pengujian hipotesis diperoleh thitung 5,325 sedangkan a = 0.05 dan db = 48, diperoleh ttabel = 2.010, sehingga thitung (5,325) > ttabel (2,010) maka dapat dikatakan H1 diterima dan H0 ditolak bahwa terdapat perbedaan pada kemampuan berpikir kritis siswa. Hasil untuk perhitungan Gain diperoleh sebesar 0,70 dengan kriteria tinggi, Sehingga terdapat peningkatan pada kemampuan berpikir kritis siwa.
Kata Kunci: IPAS, Kemampuan Berpikir Kritis, Model Research Based Learning (RBL)

This research is motivated by the low critical thinking skills of students in the Natural and Social Sciences (IPAS) subjects. The purpose of this study is to describe the effect of the Research based learning (RBL) learning model on students' critical thinking skills and the Gain on students' critical thinking skills using the Research based learning (RBL) learning model. The research subjects were 50 students. The research approach used in this study is a quantitative approach with an experimental method, namely a quasi-experiment with a nonequivalent control group design. Data collection was carried out using a test instrument in the form of pretest-posttest descriptive questions to measure students' critical thinking skills in implementing the Research based learning (RBL) learning model. Based on data analysis, the average value after being given treatment (posttest) is greater than the average value before being given treatment (pretest). Hypothesis testing obtained t count 5.325 while a = 0.05 and db = 48, obtained t table = 2.010, so t count (5.325)> t table (2.010) then it can be said that H1 is accepted and H0 is rejected that there is a difference in students' critical thinking skills. The results for the Gain calculation were obtained at 0.70 with high criteria, so there is an increase in students' critical thinking skills.
Keywords: IPAS, Critical Thinking Skills, Model Research Based Learning (RBL)