Considerations of Power, Effect Size, and Sample Size in the Planning and Analyses of Studies
Philippine Journal of Psychology
14 Pages Posted: 5 Jul 2009
Date Written: June 2007
Despite availability of softwares, power analysis has not become standard practice among researchers in psychology. In this paper, the relationships among power, significance level, sample size, and effect size are discussed. Actual research data are used to illustrate that the power of a test is increased with an increase in effect size, a decrease in significance level, and an increase in sample size. Strategies for power analysis are described. Recommendations are discussed, including choosing a sample size that ensures adequate power for a planned study, pursuing research on effects with large magnitudes rather than with only small magnitudes, and reporting effect sizes to enable readers to better gauge the importance of research results.
Keywords: Power Analysis, Effect Size, Sample Size, Null Hypothesis Testing
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