Mathematical communication is useful in developing mathematical ideas and solving mathematical problems. It is a basic ability that must be possessed by students. Therefore, the ability of mathematical communication becomes one of the important mathematical skills to be possessed and honed by each student when learning mathematics. Of course, appropriate learning models will have an effect on students' mathematical communication skills. This study aims to determine whether there is influence of cooperative learning model type Numbered Heads Together (NHT) to the mathematical communication ability of students at SMP Negeri in Ciracas Districts.
The research method used is quasi experiment (quasi experiment). The research instrument used is the test instrument of mathematical communication capability in the form of 5 description questions that have been declared valid. The target population of this study is all students of SMP Negeri in Ciracas Districts. The research sampling technique consists of two stages. The first stage is choosing teachers who teach the same classes that are class VIII-1, VIII-2, VIII-3, and VIII-4 by using simple random sampling technique. The second stage is by cluster random sampling technique, which is taking 2 of 4 classes that have passed the prerequisite test of data analysis before treatment, as experimental class (VIII-1) and control class (VIII-2).
Based on the prerequisite test results of the data analysis after the treatment, the experimental class and the control class have a normal and homogeneous distribution. Therefore, statistical hypothesis testing uses t-Test for 2 independent samples with significant level α = 0.05. Based on the calculation of statistical hypothesis, obtained tcount = 2.4646 and ttable = 1.6691. The value of tcount> ttable so that H0 rejected and obtained the conclusion that there is difference of mean score of test of mathematical communication ability of student, with mean score of test of mathematical communication ability of student of experiment class higher than control class. This shows that there is influence of cooperative learning model type Numbered Heads Together (NHT) to the mathematical communication ability of students at SMP Negeri in Ciracas Districts.