Moreover, the effect size of Cohen’s d has formula as follow:
19
d = Annotation:
d = Effect Size Cohen’s d μ
1
= mean score of group 1 μ
2
= mean score of group 2 = pooled standard deviation
There are some guidelines for determining whether the effect size is small, medium, or large.
20
Cohen suggests the following:
Table 3.1 Effect Size Range and its Category of Cohen’s d
Effect Size Range Category
0.2 Small
0.5 Medium
0.8 Large
b. If the data pretest and posttest score of the experimental and control class is normally distributed and does not have homogenous variance, the
independent sample t-test can be done. However, in reading the test, it must use the row Equal Variance Not Assumed it is assumed that the
variance is not homogenous. Then, the steps and the criteria of doing the
test is similar with the point a. above.
c. If one or both of the experimental and the control class’ data pretest and
posttest score are not distributed normally and does not meet the requirement of homogeneity test, the non parametric test with Mann-
19
Barry H. Cohen and R. Brooke Lea, Essentials of Statistics for the Social and Behavioral Sciences, New Jearsey: John Wiley Sons, 2004, p. 124
20
Ibid, p. 125
Whitney test on IBM SPSS Statistics 19 is used to test the hypothesis. Moreover, the steps of doing Mann-Whitney test and its criteria are as
follow: 1 Making the hypothesis:
H : There is no positive effct of using picture books in
students’ performance in writing narrative text.
H
1
: There is positive effct of using picture books in students’ performance in writing narrative text.
2 Calculating two independent sample with Mann Whitney or U-test on IBM SPSS Statistics 19. The steps are as follow:
21
a Open the file 2 independent samples on CD, statistic non- parametric folder
b Click Analyze = Nonparametric Test = 2 Independent Samples
on the menu until Two-Independent-Samples Test
dialogue box appears
c Fill variable on the box Test Variable List and fill another variable on the box Grouping Variable. Then choose Mann-
Whitney U test on the box Test Type
d Click Define Groups, fill the variable value on the box Group 1
and 2
e Click Continue until it comes back to the dialogue box Two
Independent-Sample Test
f Click OK
3 Making decision about significance levelprobability value p using significance degree 5 α = 0.05, the creteria in taking the decision is
as follow:
21
C. Trihendradi, op. cit., pp. 174-175
If the significance level probability valu e p ≥ α = 0.05, H
is accepted.
If the significance level probability value p α = 0.05, H
is rejected.
I. Statistical Hypothesis
The criteria of hypothesis testing which is used in this research is as follow: H
: t
count
t
table
or Sig 2-tailed
⁄
α H
1
: t
count
t
table
or Sig 2-tailed
⁄
α Explanation:
1 H Null hypothesis: There is no positive effect of using picture books in
students’ performance in writing narrative text. 2 H
1
H
a
Alternative hypothesis: There is positive effect of using picture books in students’ performance in writing narrative text.
39
CHAPTER IV FINDINGS AND DISCUSSIONS
This chapter presents the data description which consists of the score of pre- test and post-test of the experimental class and the control class. Moreover, the
discussion of the research finding is also explained in this chapter.
A. DATA DESCRIPTION
In the following description, it was presented the research finding. The finding was gained from the result of the experimental and control class’ pre and
posttest score.
1. The Score
of Both Experimental and Control Class’ Pretest
The following is the table which presented the experimental and the control class’ pretest score:
Table 4.1 The Score of the Experimental and Control Class’ Pretest
Student’ Number
Pretest Score Experimental Class
Control Class
1. 50
25 2.
22.5 27.5
3. 32.5
40 4.
30 32.5
5. 35
67.5 6.
60 62.5
7. 55
67.5 8.
35 52.5
9. 60
50
10. 55
67.5 11.
67.5 30
12. 42.5
47.5 13.
30 67.5
14. 62.5
40 15.
30 47.5
16. 27.5
45 17.
40 72.5
18. 40
32.5 19.
25 60
20. 27.5
32.5 21.
25 45
22. 30
25 23.
50 22.5
24. 42.5
22.5 25.
50 25
26. 27.5
25 Total
1052.5 1132.5
Mean 40.48
43.56
In the table above, it could be seen that the highest pretest score in the experimental class was 67.5 whereas the control one was 72.5.
However, the lowest score in both experimental and control class was 22.5. Actually, when assessing both experiment and control class’ pretest
and posttest, the researcher used The Analytic FictionNarrative Writing Content Rubric from Vicki L. Kohen and John Edwin Cowen which was
provided in the the APPENDIX 1. This analytic narrative writing content rubric gave a separate score for each aspects or categories of students’
narrative writing, for example: writing process, setting, characters, introduction
organization, sequencing
organization, transition
organization, conclusion organization, grammar and spelling, and capitalization and punctuation. The score for each aspect of students’
narrative writing was on a scale of 2.5 need improvement, 5 satisfactory, 7.5 good, and 10 excellent. Moreover, the meanaverage
of pretest score which was obtained in the experiment class was lower 40.48 than in the control one 43.56.
2. The Score
of Both Experimental and Control Class’ Posttest
The following is the table which presented the experimental and the control class’ posttest score:
Table 4. 2 The Score of the Experimental and the Control Class’ Posttest
Student’ Number
Posttest Score Experimental Class
Control Class
1. 60
35 2.
32.5 32.5
3. 50
55 4.
67.5 42.5
5. 62.5
35 6.
77.5 55
7. 62.5
67.5 8.
67.5 60
9. 70
55 10.
67.5 70
11 80
50 12.
45 55
In the table above, it could be seen that the highest posttest score in the experimental class was 80 whereas the control class was 77.5.
However, the lowest score in the experimental class was 27.5 and the control class was 32.5. Moreover, the mean of posttest score obtained by
the experimental class was 60.87, while the control class was 51.83. 13.
32.5 45
14. 77.5
32.5 15.
65 50
16. 60
77.5
17. 75
75 18.
65 45
19. 27.5
47.5 20.
57.5 50
21. 57.5
45 22.
50 45
23. 72.5
52.5 24.
72.5 60
25. 77.5
55 26
50 55
Total 1582.5
1347.5 Mean
60.87 51.83
