figure of comparison between the mean of the experimental and the control groups on the post-test.
Figure 4.2 The Mean of the Experimental and the Control Groups on Post-test The figure above showed that the students’ achievement in the
experimental group was higher than the students’ achievement in the control
group. However, the t-test was still needed. It was used to check whether the difference of the students’ data on post-test was significant or not. Before the t-
test was calculated, the normality and homogeneity of the post-test scores were analyzed first.
4.3.1 Normality of the Post-test Scores
The way to test the normality of the post-test scores was the same as in the pre- test. It used Chi Square formula. This normality test was used to know whether
the post-test scores of the two groups, the experimental and the control groups, were normally distributed or not.
20 40
60 80
100 71.32
63.89
Experimental group Control group
From the calculation, the value of X
2 data
for the experimental group was 1.18, while the value of X
2 data
for the control group was 1.15. Meanwhile, the value of X
2 table
with degrees of freedom dk = k – 3 = 6 – 3 = 3 and α = 5 is
7.81. The data are said to have a normal distribution if the value of X
2 data
were equal to or lower than the value of X
2 table
. Since the value of X
2 data
for the experimental group 1.18 and the control group 1.15 were lower than the value of X
2 table
7.81, it meant that the post-test scores for both of groups were said to be normally distributed. The complete
result of the X
2
calculation of post-test scores could be seen in appendix 15 for the experimental group and in appendix 16 for the control group.
4.3.2 Homogeneity of the Post-test Scores
In this research, F test was used in order to see whether the two variances of the post-test scores in experimental and control groups fulfilled the condition of
homogeneity or not. The way to test the homogeneity of the post-test scores was also the same
as in the pre-test. First, the variance of each group was calculated. The variance of the experimental group Ve was 288.09, and the variance of the control group
Vc was 214.83. After that, the higher variance was divided by the lower variance to get the F
data
. The calculation was as follows:
From the calculation, the value of F
data
for the post-test scores was 1.34. Meanwhile, the value of F
table
with dk numerator V
1
= n
1
– 1 = 28 – 1 = 27, dk denominator V
2
= n
2
– 1 = 28 – 1 = 27 and α = 5, squared to V
1
= 28 and V
2
= 28 is 1.87. The data are said to be homogenous if F
data
F
table
. Since the value of F
data
was lower than the value of F
table
, it could be concluded that the variances of the post-test scores in experimental and control
groups fulfilled the condition of homogeneity. The complete calculation of the F test for the post-test scores could be seen in appendix 19.
4.3.3 T-test for Post-test
