THE IMPLEMENTATION OF COOPERATIVE LEARNING MODEL TYPE NUMBER HEAD TOGETHER TO IMPROVE THE STUDENTS MATHEMATICAL COMMUNICATION ABILITY OF EIGHTH GRADE SMP N 2 SIDIKALANG ACADEMIC YEAR 2014/2015

The purpose of this research were (1) to find out how the Number Head Together learning model can improve the students' mathematical communication ability, (2) to describe the process of answer toward mathematics learning by using Number Head Together learning model. The type of his research was belongs to Classroom Action Research (CAR), which is implemented in SMP Negeri 2 Sidikalang. The subjects in this research were students of VIII-1 class in academic year 2014/2015 that have total of 39 students consisted of 9 male and 30 female. The object of this resarch were the students’ mathematical communication ability and Number Head Together learning model. This research consisted of 2 cycles and each cycles consists of 2 meetings. Students' mathematical communication ability test conducted at the end of each cycle. Instrument used to collect the data is mathematical communication ability test with the form of essay test as many three problems, and observation sheet. The results of this study can be seen: (1) The results of students’ mathematical communication ability test in the first cycle known average value of 61.82, 15 students were completed and 24 students were uncompleted, the classical completeness was 38,46% and the students’ mathematical communication ability was categorized to low category categorized. (2) The results of students’ mathematical communication ability test in the second cycle known average value of 78.63, 35 students were completed and 4 students were uncompleted, the classical completeness was 89.74% and the students’ mathematical communication ability was categorized to good category. (3) Learning by using the Number Head Together learning model can make students’ activity were good categorized in learning, and (4) Learning by using the Number Head Together learning model can make the process of student’s answer more varied. From the results of this research can be concluded that the implementation of the Number Head Together learning model can improve the students’ mathematical communication ability. The suggestion that given for teachers is to be able to implement the Number Head Together learning model as an alternative in the learning process that can improve mathematical communication ability.