Arab Educational Information Network

This study aimed at analyzing of the statistical power and its relation to the significance level and the effect size. The sample of the study consisted of (90) published researches in the Journal of Research in Education and Psychology from (2010) to(2012). The results showed that (72%)of the hypotheses had been rejected and the means of their statistical power was(0.22),the other (28%) of the hypotheses had been accepted and the means of their statistical power was(0.92), the ratio of using the effect size with the significance level for "t-test" was(20%), the analysis of variance was(5%),the correlation coefficient was(zero),the statistical of Non parameter was(3.3%), and the analysis of regression was(1.6%). The levels of the effect size for the significant hypotheses using "t-test" were (17%)low,(11%)medium, and (72%)high where the levels of the effect size for the insignificant hypotheses using "t-test" were (95%)low ,(1.2% ) medium, and (3.6%)high , the analysis of variance for the significant hypotheses was (78%)low,(11%)medium,(11%)high whereas the analysis of variance for the insignificant hypotheses was(100%) weak. The results also showed a significant correlating relation between the statistical power and the both of the effect size and the significance level. (Published abstract)