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Estimation of Type III Error and Power for Directional Two-Tailed Tests Using PROC POWER

Overview By imposing directional decisions on traditional two-tailed tests, one will overestimate power, underestimate sample size, and ignore the risk of Type III error. A person can avoid these problems by using the directional two-tailed test. This paper demonstrates how to use PROC POWER to estimate the prospective power and Type III error for one-sample, two-sample and paired t tests for means, and binomial tests for proportions, using the directional two-tailed testing procedure. Examples are given with SAS codes accompanied by selected results. Power and Type III error for the directional two-tailed sign test with unknown direction is also discussed and illustrated with a SAS macro written by the author.

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PublisherSAS Institute File FormatPDF
Date PublishedMarch 2005
FormatWhite Papers   
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