ΣY = Σy − Σy
Ny
ΣY = 5632 − 416.0
36 ΣY = 5632 − 4807.11
ΣY = 824.89 To make the analysis more reliable, I analyzed by using t-test formula as
stated in chapter III.
4.4 Test of Significance
As mentioned above, the mean of control group was lower than the mean of the experimental group. Nevertheless, I could not infer that the difference between the
two means was significant. Hence, I applied t-test formula. T-test was used to check whether the two means were statistically significant or not. Here is the
formula:
t = Mx
− My ΣX + ΣY
Nx + Ny − 2
1 Nx
+ 1
Ny Where :
Mx = the mean score of experimental group
My = the mean score of control group
Nx = the number of students of experimental group
Ny = the number of students of control group
X
2
= the total square deviation of the experimental group Y
2
= the total square deviation of control group
t = Mx
− My ΣX + ΣY
Nx + Ny − 2
1 Nx
+ 1
Ny Where:
ΣX = Σx − Σx
Nx
ΣX = 9776 − 476
31 ΣX = 9776 − 7308.90
ΣX = 2467.10
And ΣY = Σy −
Σy Ny
ΣY = 5632 − 416.0
36 ΣY = 5632 − 4807.11
ΣY = 824.89
So the t value could be computed as follow:
t = 15.35
− 11.56 2467 + 825
36 + 31 − 2
1 36
+ 1
31 =
3.80 3292
65 67
1116 =
3.80 1.74
t = 2.18
As suggested by Best 1981, “for subjects which require fixed computation such as mathematics and physics the 1 percent 0.1 alpha level of significance
can be used. Whereas the psychology and educational cycles the 5 percent 0.5 alpha level of significance can be used.” So, I used the 5 percent 0.5 alpha level
of the significance. The number of the subjects from both control and experimental group was
67, so the degree of freedom was 65, which were obtained from: ∑Nx+∑Ny-2. For 5 percent 0.5 alpha level and 65 degree of freedom was no
definite critical value in the t-table. It was needed to find the definite value using interpolation.
t-table for 40 = 1.684 60 = 1.671
65 = ...? 40
− df df
− 60 =
1.684 − t
t − 1,671
40 − 65
65 − 60
= 1.684
− t t
− 1.671 t = 1.67
The critical t-value was 1.67. The obtained t-value from the t-test calculation above was 2.18. Therefore, it could be shown that the obtained t-
value was higher than the critical t value. It could be inferred that there was significant difference between experimental and control group.
4.5 Discussion of Research Findings
