Implications of statistical power for confidence intervals.
The statistical power of a hypothesis test is closely related to the precision of the accompanying confidence interval. In the case of a z-test, the width of the confidence interval is a function of statistical power for the planned study. If minimum effect size is used in power analysis, the width of the confidence interval is the minimum effect size times a multiplicative factor φ. The index φ, or the precision-to-effect ratio, is a function of the computed statistical power. In the case of a t-test, statistical power affects the probability of achieving a certain width of confidence interval, which is equivalent to the probability of obtaining a certain value of φ. To consider estimate precision in conjunction with statistical power, we can choose a sample size to obtain a desired probability of achieving a short width conditional on the rejection of the null hypothesis.
Department of Educational Studies, University of South Carolina, Columbia, SC 29208, USA. xliu@mailbox.sc.edu
Xiaofeng Steven
XS
Liu
D015928:Cognitive Behavioral Therapy / Q000706:statistics & numerical data; D016001:Confidence Intervals; D006801:Humans; D006973:Hypertension / Q000628:therapy; D008960:Models, Psychological; D015233:Models, Statistical; D012107:Research Design / Q000706:statistics & numerical data*; D018401:Sample Size; D013315:Stress, Psychological / Q000628:therapy