The score of 69.91 for attitude towards probability in post-test 1 of the experimental group is higher, compared to the score of 61.00 for the control group. This study shows that there is a significant effect of cooperative TGT in the effort to increase students’ attitude towards probability. The score of 69.91 by the experimental group on attitude towards probability in post-test 1 decreased to 61.19 for post-test 2 and this was also due to the conventional approach (figure 2)