By using such formula, the homogenity of pre‐test of the experimental group and
control group is calculated as follows:
4632 .
1 98.67
144.37 F
= =
Then, the result was consulted with the value of F table with dk numerator v
1
= 25 – 1 =
24, dk numerator v
2
= 25 ‐1 = 24, and α = 0.05, squared to v
1
= 25 and v
2
= 25, which is
2.27. It could be considered that the data were homogeny for the F value 1.4632 F
table 2.27.
The result of the post‐test of those two groups was also computed with the same
formula in calculating the homogeneity as follows:
4103 .
1 52.00
73.33 F
= =
The result was also consulted with the value of F table with dk numerator v
1
= 25 – 1 =
24, dk numerator v
2
= 25 ‐1 = 24, and α = 0.05, squared to v
1
= 25 and v
2
= 25, which is
2.27. Since the F value 1.4103 F table 2.27, the post test of the experimental and
control groups were also said to be homogeny. The computation of homogenity can be
seen in Appendices 17 and 22.
4.3.3 Mean Difference Test
In order to identify the significant difference between the experimental and control
groups, the means of the two groups should be compared. The data being compared
were the difference between the two means of the pre‐test and post‐test for the result
of the treatment could be seen through those data.
The difference between the two means was computed by using the formula
stated by Arikunto 2002:264 below:
e X
=
Ne Xe
∑ c
X
=
Nc Xc
∑
The mean of the experimental group on pre‐test is
e X
=
Ne Xe
∑
= 1460 = 58.40 25
The mean of the post‐test of the experimental group is
e X
=
Ne Xe
∑
= 1860 = 74.40 25
Whereas, the mean of the pre‐test of the control group is
c X
=
Nc Xc
∑
= 1476 = 59.04 25
The mean of the control group on the post‐test is
c X
=
Nc Xc
∑
= 1740 = 69.60 25
The calculation above shows that the mean score of the experimental group on the pre‐
test was 58.40 and the post‐test was 74.40. From those scores, the different mean
between pre‐test and post‐test of the experimental group was 16. Meanwhile, the pre‐
test and post‐test scores of the control group were 59.04 and 69.60, with the difference
between two means fell at 10.56 points. It could be seen that the different mean of the
experimental group is higher than the control group.
It, therefore, could be concluded that there is good improvement of the experimental
group after having been given treatment by using documentary films in BBC
VCD in writing report text. Yet, it had not been concluded that the difference between
two means of the pre‐test and post test was significant. Thus, the t‐test formula
was applied in determining whether the difference of the two means was statistically
significant or not.
4.3.4 The T‐Test Analysis
The study was conducted to investigate whether there is any significant difference of
ability in writing report text between the students taught by using documentary films in
BBC VCD and without using documentary films in BBC VCD as media in teaching writing,
particularly report text. It was hypothesized that there is significant mean difference
between the experimental and control groups.
The t‐test was applied to measure the significance between pre‐test and post‐ test
of the experimental group and the control one. Yet, the standard deviation should be
computed first before applying the t‐test. The formula is as follows:
Thus:
2 25
25 840
. 47
1 25
667 .
74 1
25 s
− +
− +
− =
2 n
n 1
n 1
n s
2 1
2 2
2 2
1 1
− +
− +
− =
s s
48 16
. 1148
008 .
1792 s
+ =
2535 .
61 s
=
= 7.83
Afterwards, the t‐test formula was applied to measure the significant difference between
the experimental and control groups as follows:
2 1
n 1
n 1
s x
x t
2 1
+ −
=
Therefore,
25 1
25 1
7.83 56
. 10
16 t
+ −
=
2.2115 44
. 5
t =
= 2.442
Then, the t‐value obtained from the computation should be consulted with the critical
value in the t‐table before verifying the hypothesis. The 5 0.05 level of significant was
used. If the t‐value is higher than the t‐table, it means that there is significant difference
between the two means of the experimental and control groups. On the contrary, if the
t ‐value is lower than the t‐table, meaning that there is no significant difference between
the two means.
The number of subject in this study for the experimental and control groups were
50 with the degree of freedom df = Nx + Ny – 2 = 25 + 25 – 2 = 48. At the 5 0.05
alpha level of significance, the obtained t‐value was 2.442 and t‐table was 2.01 see
Appendix 26. The result shows that t‐value is higher than the t‐table, proving that there
is significant difference between the students’ achievement of the experimental group
and control group. Therefore, there is significant difference between the students who
were taught by using documentary films in BBC VCD and without using documentary
films in BBC VCD in teaching writing report. In
could be concluded that the research findings revealed that the result of the treatment
by using documentary films in BBC VCD proved the hypothesis that “Documentary
films in BBC VCD is effective in improving students’ ability in writing report
texts at the eleventh grade students of SMA Negeri 2 Wonosobo, in the academic year
20102011.” Therefore, the null hypothesis that “Documentary films in BBC VCD is not
effective in improving students’ ability in writing report texts at the eleventh grade students
of SMA Negeri 2 Wonosobo, in the academic year 20102011” was unproved and
rejected.
4.4 Discussion of the Research Findings
