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Sample size determination for repeated measures design using G Power software
Anesth Pain Med 2015;10(1):6-15
Published online January 31, 2015
© 2015 The Korean Society of Anesthesiologists.

Hyun Kang
Department of Anesthesiology and Pain Medicine, Chung-Ang University College of Medicine, Seoul, Korea
Correspondence to: Hyun Kang
Received October 8, 2014; Accepted December 19, 2014.
cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Repeated measures designs are widely used in the field of anesthesiology because they allow the detection of within-person change over time and provide a higher statistical power for detecting differences than a single measure design while reducing the costs and efforts to conduct a study. However, the complex process of calculating the sample size for repeated measures design requires profound statistical knowledge and also programming skills in some instances. In the present article, the author describes 1) the basic statistics for repeated measures design, 2) the explanation for G Power software, and 3) how to calculate the sample size using an example. (Anesth Pain Med 2015; 10: 6-15)
Key Words : G Power, Power calculation, Repeated measures design, Sample size determination, Sphericity
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