ABSTRACTFenti Saktiyani, S891308015. The Effectiveness of Group Investigation to Teach SpeakingViewed from Students’ Self-Confidence (An Experimental Study at the Tenth Grade of SMAMuhammadiyah 2 Yogyakarta in the Academic Year of 2014/2015). First Consultant: Dr.Ngadiso, M.Pd; Second Consultant: Dr. Slamet Supriyadi, M.Pd. Thesis. English Department,Graduate School, Sebelas Maret University, Surakarta, 2014.This research is aimed at finding out whether: (1) group investigation is more effectivethan direct instruction in teaching speaking at the tenth grade students of SMA Muhammadiyah 2Yogyakarta in the academic year of 2014/2015; (2) ten grade students having high selfconfidencehave better speaking skill than those having low self-confidence; and (3) there is aninteraction between teaching method and students’ self-confidence to teach speaking.The researcher employed experimental study in conducting this research. The populationof this research was tenth grade students of SMA Muhammadiyah 2 Yogyakarta in the academicyear of 2014/2015. The sample consisted of two groups; experimental groups (X MIA 5)consisting of 28 students and control group (X MIA 3) consisting of 28 students. Those twogroups were taken by using cluster random sampling. The researcher used self-confidencequestionnaire and speaking test as the test instrument of this research. The researcher carried outseveral steps for collecting data, namely: The first step was giving the questionnaire to thestudents to measure their self-confidence. The second step was treatment where the teachingmethod was applied in eight meetings of each class. The third step was post test. The studentswere given post test using speaking test. The research data were gained using speaking test andself-confidence questionnaire. They were analyzed in the terms of descriptive statistics andinferential statistics including normality and homogeneity. The data was analyzed using ANOVAtest (Multifactor Analysis and Variance) and Tukey test.The research findings indicate that: (1) group investigation is more effective than directinstruction to teach speaking in the tenth grade students of SMA Muhammadiyah 2 Yogyakartain the academic year of 2014/2015; (2) the students having high self-confidence have betterspeaking skill than those having low self-confidence; and (3) there is an interaction betweenteaching methods used in this research and the students self-confidence levels in teachingspeaking.Regarding to the research findings, it can be concluded that group investigation iseffective to teach speaking at the tenth graders of SMA Muhammadiyah 2 Yogyakarta in theacademic year of 2014/2015. This result of the research recommends for the teacher to use groupinvestigation method as an alternative teaching methods in teaching speaking skill. It alsorecommends that the further researcher can use this research as the reference of the research.Keywords : speaking, group investigation, direct instruction, self-confidence, experimental study