International Journal on Emerging Mathematics Education (IJEME) Vol. 3, No. 2, September 2019, pp. 129-138 P-ISSN: 2549-4996, E-ISSN: 2548-5806, DOI: http://dx.doi.org/10.12928/ijeme.v3i2.13806 Received August 5, 2019; Revised August 25, 2019; Accepted August 30, 2019 The Effectiveness of Geogebra’s Metacognitive Guidance to develop Critical thinking skills Heris Hendriana, Wahyu Setiawan, Usman Aripin IKIP Siliwangi, Jl. Terusan Jenderal Sudirman, Cimahi, Jawa Barat, Indonesia e-mail: herishen@ikipsiliwangi.ac.id Abstract This research is a quasi-experimental study aiming at analyzing the role of the metacognitive guidance approach in order to improve high-school students' critical thinking skills by applying Non-Equivalent Control Group Design. This study involved high school students in one of the high schools in the city of Cimahi. In this study, the pretest for mathematical critical thinking skills is administered to two classes of students of control and experiment groups. The experimental group uses the metacognitive guidance approach assisted by GeoGebra software, whereas the control group uses the conventional method. Both classes receive the same hours of study, mathematics teacher as well as mathematics contents. The researcher conducted observations only in the experimental class. At the end of the treatment, a post-test for the two groups was carried out regarding students’ mathematical critical thinking skills included processing the results of the test, namely the data. After this research has been carried out, the next step is to analyze the data and draw conclusions of the research. In analyzing the data, it is categorized into three levels, namely high, medium and low abilities. The data is analyzed by means of t-test to test the difference of two means of students’ critical thinking ability. Data analysis was performed using the SPSS software. The analysis shows that there is a significant difference in mathematics critical thinking ability between the two groups of students. Keywords: Critical thinking skills, Geogebra’s Metacognitive Guidance How to Cite: Hendriana, H., Setiawan, W., Aripin, U. (2019). The Effectiveness of Geogebra’s Metacognitive Guidance to develop Critical thinking skills. International Journal on Emerging Mathematics Education, 3(2), 129-138. http://dx.doi.org/10.12928/ijeme.v3i2.13806 INTRODUCTION Mathematics is one of the most important subjects to be mastered because almost every level of mathematics education is studied. Besides mathematics is closely related to daily life according to their respective capacities, such as traders who use their arithmetic abilities, architects with their measurements, astronomy with their predictions, etc. Like using percent, many people use percent in many jobs and activities in their daily lives (Aripin, Setiawan & Hendriana, 2019; Hidayat & Aripin, 2019; Putri & Zulkardi, 2019). Mathematical critical thinking is the basis of the process of thinking to analyze arguments and bring ideas to each meaning to develop logical thinking patterns. It was also expressed by (Marlina & Harahap, 2018) that mathematical critical thinking is a process that leads to drawing conclusions about what we have to believe and actions to be taken. According to (Sari, Eriani, Audina, & Setiawan, 2019), mathematical critical thinking is an activity of thinking about ideas or ideas related to a given concept or problem. Meanwhile, according to Ennis (Senjayawati, 2018) mathematical critical thinking is a process of thinking with the aim of making sensible decisions about what is believed to be truth can be done correctly. From some of the expert