The figure above showed that the students’ achievement of both groups were relatively the same before they were given the treatment. In order to prove
that there were similarities in pre-test data in the experimental and the control groups, t-test was needed. However, before the t-test was calculated, the normality
and homogeneity of the pre-test scores were analyzed first.
4.1.1 Normality of the Pre-test Scores
This normality test was used to know whether the pre-test scores of the two groups, the experimental and the control groups, were normally distributed or not
by using Chi Square formula. From the calculation, the value of X
2 data
for the experimental group was 2.59, while the value of X
2 data
for the control group was 6.09. 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 2.59 and the control group 6.09 were lower than the value of X
2 table
7.81, it meant that the pre-test scores for both of groups were said to be normally distributed. The complete
result of the X
2
calculation of pre-test scores could be seen in appendix 13 for the experimental group and in appendix 14 for the control group.
4.1.2 Homogeneity of the Pre-test Scores
In this research, F test was used in order to see whether the two variances of the
pre-test scores in experimental and control groups fulfilled the condition of homogeneity or not.
First, before the F test was obtained, the variance of each group was calculated. The variance of the experimental group Ve was 430.03, and the
variance of the control group Vc was 236.40. Then, to get the F
data
, the higher variance was divided by the lower variance. The calculation was as follows:
From the calculation, the value of F
data
for the pre-test scores was 1.82. 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 pre-test scores in experimental and control
groups fulfilled the condition of homogeneity. The complete calculation of the F test for the pre-test scores could be seen in appendix 17.
4.1.3 T-test for Pre-test
