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more, the instrument was reliable. The instrument reliability was estimated by using Cronbach Alpha reliability test. Ba
sed on the results, the value of α was 0.939. The table shows that the instruments used in this study have a high
level of reliability. The calculations were done using a computer program SPSS version 21.
The result of the reliability test can be seen in Table 10.
Table 10: The Reliability Score Cronbach’s Alpha N of items
0.939 2
2. Description of Research Data
There were two classes which were used as the subjects of the study. The first class was VIII B as the experimental group and the second one was VIII A as
the control group. They were chosen by clustering. The experimental group was given picture series as the media in teaching writing and the control group was
given text book as conventional technique the teacher often used, the writing based text book. Before and after giving the treatments to both groups, the
researcher conducted tests to get the scores of students’ writing ability. Both control and experimental groups were given two types of test. They were the pre-
test, the test before giving the treatments, and the post-test, the test after conducting the treatments. After obtaining the pre-test and post-test scores from
experimental and control groups, the researcher made the categorization of students’ writing scores.
In making the categorization of students’ writing ability scores, ideal mean
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Mi and ideal standard deviation Sdi had to be found first. Mean was the average score of the students’ scores and it could be found by adding all the
students’ scores and divided them by all the number of the students. Meanwhile, standard deviation was a measurement of how the scores spread out. In this
categorization section, the researcher divided it into four main parts. They were the categorization of experimental group’s pre-test, the categorization of
experimental group’s post-test, the categorization of control group’s pre-test and the categorization of control group’s post-test. The result of descriptive statistic
can be seen in Table 10.
Table 10: Descriptive Statistic
N Minimum
Maximum Mean Std.Deviation
Pretest experimental Pretest control
Posttest experimental Posttest control
Valid N list wise 32
32 32
32 32
17.00 16.00
18.00 18.00
23.00 20.00
23.00 22.00
19.6563 18.5626
21.0625 19.6563
1.97744 1.34254
1.60518 1.12478
