TEST POWER IN COMPARISON DIFFERENCE BETWEEN TWO INDEPENDENT PROPORTIONS

In this study, the effect of population proportion difference (effect size) and the relation between sample sizes on test power in comparing two independent proportions were investigated. At the end of 50 000 simulation experiments it was observed that increasing in the sample size and population proportion difference increase the test power while the controversy decreases it. In the case of studies with equal sample sizes, sufficient test power level (80.0 %) was obtained by 60, 90, 150 and 350 observations when = 0.25, 0.20, 0.15 and 0.10, respectively. On the other hand, it is not available to obtain sufficient power level even for the extremely large sample size taken into consideration (500 observations) when =0.05. Results of this study showed that the inequality in sample size or relations between sample sizes (n2=r.n1 or n1=r.n2) affect the test power. However, total number of observations may be more effective on the test power rather than inequality in sample sizes.