This research aimed to find out the influence of cooperative learning of STAD toward student’s understanding of mathematical concept. This research was quasi experiment with posttest control design. The research population was the whole of 7th grade student in first semester of SMPN 8 Bandar Lampung, with two classes as a sample of the research which was taken by using the purposive sampling technique. Research instrument was concept comprehension test and data analysis technique by using t-test. The results showed that cooperative learning of STAD positively influenced the student’s understanding of  mathematical concept. Keywords   : understanding of mathematical concept, cooperative learning, influence, STAD
                        
                        
                        
                        
                            
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