Homogeneity Test Click Analyze = Compare Means = One-Way ANOVA on

After calculating and obtaining the result of the independent sample t test of both the experimental and the control class’ pretest, the last step was to do hypothesis test. Additionally, there were three alternatives that can be done to test the hypothesis: a. If the data pretest and posttest score of the experimental and the control class was normally distributed and had homogenous variance, the independent sample t-test could be done. The steps of doing the independent sample t-test and its criteria were as follow: 1 Formulating the hypothesis: H : There was no positive effect of using picture books in students’ performance in writing narrative text. H 1 : There was positive effect of using picture books in students’ performance in writing narrative text. 2 Calculating t value by using the Independent Sample t-Test on IBM SPSS Statistics 19. The steps of doing the independent sample t-test are similar to the point b. above. 3 Making decision about t value on the row Equal Variance Assumed it is assumed that the variance is homogenous and using the significance degree 5 α = 0.05. The criteria of taking decision were: If t count t table or Sig 2-tailed ⁄ , H was accepted. Meanwhile, H was rejected if t count t table or 2-tailed ⁄ α. 4 Determining the effect size by using Cohen’s d. The effect size is used to identify the strength of the final part of two group differences or the relation between two variables in a quantitative study. 18 18 John W. Creswell, Educational Research-Planning, Conducting, and Evaluating Quantitative and Qualitative Research, New Jearsey: Pearson Educatio, 2008, p. 203 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