From the chart above, the different average score between the control and experimental groups was shown. In the control group, the average score of the
pre-test was 65.07 and the post-test 76.67. From those scores, the different average score between the pre-test and the post-test of the control group was
11.60. While, in the experimental group, the average score of the pre-test was 65.47 and the post-test was 84.00. The different average score between those tests
was 18.53. It meant that the different average score of the experimental group was higher than in the control group.
It could be concluded that there was improvement of the experimental groups achievement after they received the treatment using BBC Nature video. It
was also proven by the t-test formula. The result showed that there was a significant difference between the control and experimental groups on their
writing product. The computation can be seen in Appendix.
4.2 Normality and Homogenity
After the data were gathered, the normality and the homogeneity should be checked in order to know if the data could be analyzed.
4.2.1 Normality
Before the t-test computation, it was needed to make sure that the data were normal. Research data tabulation can be found in appendix.
After getting the data of the control and experimental groups, the normality of those data were analyzed. It was found that the X
2
hitung of pretest and posttest of the control group was 1.822395 and 5.54864807, while the
X
2
hitung of pretest and posttest of the experimental group was 3.681975and 4.714604.
Then, the results were consulted with critical value of X
2
hitung α dk
with α = 0.05 and dk = 3, whose result is 7.815. Since the value of X
2
hitung α
dk of the control and experimental groups were lower than 7.815, the data were considered to be normally distributed.The computation of normality can be seen
in Appendices.
4.2.2 Homogenity
Homogenity is important to check whether the data of each group are homogeny or not. The computation of homogeneity goes as follow:
F = Ve
Vc
Use the formula stated above, the homogeneity of pre-test of the experimental and control groups is computed as follow:
F = Ve
Vc
= 72.25747126
47.37471264
= 1.525232919
The value of F table with dk numerator V1 = n1 - 1 = 30 - 1 = 29, dk denominator v2 = n2-1 = 30 -
1 = 29 and α = 5, squared to V1 =30 and V2 = 30
is 1.85. Because F hitung 1.53 1.85 then we can conclude that the data of both pretest is homogeny.
While the homogeneity of post-test of both groups was computed as follow:
F = Ve
Vc
= 50.75862069
56.36781609
= 0.900489396
The value of F table with dk numerator V1 = n1 - 1 = 30 - 1 = 29, dk denominator v2 = n2-1 = 30 -
1 = 29 and α = 5, squared to V1 =30 and V2 = 30 is 1.85. Because F hitung 0.90 1.85 then we can conclude that the data of both
pretest is homogeny.The computation of homogenity can be seen in Appendices.
4.3 Difference between the Two Means
