Penelitian ini bertujuan untuk mengetahui pengaruh model pembelajaran Kooperatif Tipe Group Investigation (GI) terhadap kemampuan pemahaman konsep matematika siswa kelas VII SMP Negeri 2 Tarakan. Penelitian ini dilaksanakan pada tanggal 16 Januari–25 Januari 2017 di SMP Negeri 2 Tarakan.
Jenis penelitian ini adalah Quasi Exsperimental Research dengan desain posttest only control design. Populasi dalam penelitian ini adalah seluruh kelas VII SMP Negeri 2 Tarakan. Sampel penelitian ini adalah kelas VII-J sebagai kelas eksperimen dan VII-I sebagai kelas kontrol, Sampel penelitian diambil dengan teknik simple random sampling. Teknik pengumpulan data dalam penelitian ini menggunakan tes. Data dianalisis menggunakan analisis statistik deskriptif dan analisis statistik inferensial. Analisis deskriptif meliputi rata-rata hitung dan simpangan baku. Analisis statistik inferensial menggunakan uji statistik independent sample t- test dengan bantuan software SPSS versi 16.0 for windows.
Hasil analisis deskriptif menunjukkan bahwa nilai rata-rata kemampuan pemahaman konsep matematika kelas eksperimen adalah 81,23 dan nilai rata rata kemampuan pemahaman konsep matematika kelas kontrol adalah 65,94. Sedangkan berdasarkan hasil analisis uji independent sample t-test dengan taraf signifikan 5% (a = 0,05) diperoleh p-value sebesar 0,000. Sehingga dapat dilihat bahwa 0,000 < 0,05. Dengan demikian H0 ditolak dan H1 diterima, artinya nilai rata-rata kemampuan pemahaman konsep matematika siswa pada kelas eksperimen lebih tinggi secara signifikan dari nilai rata-rata kemampuan pemahaman konsep matematika siswa pada kelas kontrol. Sehingga dapat disimpulkan terdapat pengaruh model pembelajaran kooperatif Tipe Group Investigation (GI) terhadap kemampuan pemahaman konsep matematika siswa pada kelas VII SMP Negeri 2 Tarakan.

Kata Kunci: Group Investigation (GI), Kemampuan Pemahaman Konsep Matematika

The objective of this study is to find out the effect of guided cooperative learning model type Group Investigation (GI) toward mathematic student's concept understanding at the seven-grade class of SMP Negeri 2 Tarakan. This research was held on 16 January – 25 January 2017 in SMP Negeri 2 Tarakan. The type of this study is Quasi Experimental Research by posttest only control design. The population of this study is all the seven-grade students of SMP Negeri 2 Tarakan. The sample of this study is class VII-J as an experimental and class VII-I as a control group. The sample was taken by using simple random sampling. This study used test in collecting the data. The technique of data analysis is descriptive and inferential analysis. Descriptive analysis included the mean and standard deviation. Inferential analysis which using independent sample t-test with helped by software SPPS version 16.0 for windows. Descriptive analysis showed that the average score of the ability of understanding mathematic concepts experimental class was 81,23 and the average score of the ability of understanding the mathematic concept of control class is 65,94. While, based on the analysis of test independent sample t-test with significance level of 5% (a = 0,05) obtained p-value is 0,000. So it can be seen that 0,000 < 0,05. It means that H0 was rejected and H1 was accepted. That means, that average ability of the mathematics students concept understanding in the experimental class was significantly higher than the average in the control class. So that, it can be conclude there are significantly cooperative learning model type Group Investigation (GI) of the ability of understanding mathematics concept at the seven grade students of SMP Negeri 2 Tarakan. Keywords: Group Investigation (GI), Mathematic Concept Understanding