Abstract :
The objective of this study is to know that wether the effect of the model of group learning investigation on student?s ability to slove the problem in studying mathematic at SMPK St. Yoseph Naikoten Kupang. The sampleof this study are the student of SMPK St. Yoseph Naikoten Kupang on grade VII F which numbered 33 students. The data that used in this study were pretest score and posttest score of class experimental with the model of Group Investigation. The data gotten were analized by SPSS version 22.0 program. Before Hypothesis Test, the researcher conducted a preconditional test such as: Normality Test for pretest data and posttest data. The result of data analized for pretest such as Sig.(2-tailed) = 0.065>0.05 and D??????? = 0.148<0.23> = D????? , therefore H0 accepted and it can be concluded that the data were normaly distributed. While the data of posttest was Sig.(2-failed) = 0.064>0.05 and D??????? = 0.148<0.237 = D????? . Thus H0 accepted and the data were normaly
distributed. Hypothesis testing using a paired sample test, after the data were analyzed the result was sig.(2-tailed) = 0.00 <0.05) and ?????? = 16209 > 2.03693 = ?????? , then H0 is rejected. Therefore it can be concluded that there was a significant influence of the setting interactive learning cooperatively towards mathematics achievement of junior high school students. The result showed that the model of group investigation have the effecton students ability to solve the problem in mathematic lerning proccess. Thus, the writer suggests to other mathematic teachers to use the model of group investigation in teaching and learning proccess in the classroom.