Statistical power is important in a meta-analysis study, although few studies have examined the performance of simulated power in meta-analysis. The purpose of this study is to inform researchers about statistical power estimation on two sample mean difference test under different situations: (1) the discrepancy between the analytical power and the actual power and (2) the influence of unequal sample size and unbalanced design on the power. Results indicated that there are noticeable discrepancies between the estimated power and actual power under certain conditions. In general, unbalanced design decreases the statistical power in the meta-analysis. Recommendations are provided for researchers who are interested in power of meta-analysis. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]