The aim of this research was to identify whether students' mathematical critical
thinking ability using Group Investigation learning with IDEAL problem solving
strategy was better than students' mathematical critical thinking using Group
Investigation learning. The research method used was True Experimental Design,
and sampling technique used was Cluster Random Sampling. Population of
research was all sixth grade students at SMP Negeri 4 Sumbang in the academic
year 2016/2017, while the research sampling was class VII A and VII B. Based on
the result of hypothesis testing on the data results of post test, it can be concluded
that students' mathematical critical thinking ability using Group Investigation
learning with IDEAL problem solving strategy was better than students'
mathematical critical thinking using Group Investigation learning.