<![CDATA[Penelitian ini bertujuan untuk mendeskripsikan keefektifan pendekatan open ended dan group investigation serta perbedaan keefektifan antara kedua pendekatan tersebut, ditinjau dari komunikasi dan pemecahan masalah matematis, serta motivasi belajar matematika siswa. Jenis penelitian ini adalah quasi experiment dengan desain pretest-posttest with nonequivalent group design. Populasinya adalah seluruh siswa kelas VIII SMP Negeri 1 Galur, Kulon Progo, DIY tahun pelajaran 2012/2013. Dua kelas diambil sebagai sampel, kemudian secara acak ditentukan kelas dengan perlakuan pendekatan open ended dan group investigation. Data dikumpulkan dengan tes dan non tes, dianalisa dengan one sample t-test untuk menentukan keefektifan, Hotteling t’s Trace dan uji t univariat dengan kriteria Bonferroni untuk menguji perbedaan keefektifan antara kedua pendekatan tersebut. Hasil penelitian menunjukkan bahwa pendekatan open ended dan group investigation efektif, pendekatan open ended lebih efektif dibanding pendekatan group investigation, serta pendekatan group investigation lebih efektif dibanding pendekatan open ended ditinjau dari komunikasi matematis dan motivasi belajar matematika siswa.Kata Kunci: open-ended, group investigation, komunikasi matematis, pemecahan masalah, motivasi belajar. The Effectiveness Comparison of the Open-Ended and GI Approaches Viewed from Mathematical Communicative and Problem Solving and Learning Motivation AbstractThis study aimed to describe the effectiveness of the open-ended and the group investigation approaches and the effectiveness differences between the two approaches viewed from the mathematical communicative problem-solving and the mathematics learning motivation on the basic competency of polyhedral. This research was a quasi experiment using pretest-posttest with nonequivalent group design. The population was all eighth grade students of SMP Negeri 1 Galur, Kulon Progo, Yogyakarta in 2012/2013. Two classes were taken randomly as sample, then the classes were determined randomly using the open-ended and group investigation approaches. The data was collected using test and non-test, analyzed using one sample t-test to determine the effectiveness and also analyzed using Hotteling t's Trace t-test univariate using Bonferroni criteria to determine the effectiveness difference between the two approaches. The results indicated that the open-ended and group investigation approaches were effective, the open-ended was more effective than the group investigation, and the group investigation was more effective than open ended viewed from the mathematical communicative and mathematics learning motivation.Keywords: open-ended, group investigation, communication, problem solving, mathematics learning motivation]]>
