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Epidemiology. 2018 Sep;29(5):599-603. doi: 10.1097/EDE.0000000000000876.

Planning Study Size Based on Precision Rather Than Power.

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From the Research Triangle Institute, Research Triangle Park, NC.
Boston University School of Public Health, Boston, MA.
Department of Epidemiology and Department of Statistics, University of California, Los Angeles, CA.


Study size has typically been planned based on statistical power and therefore has been heavily influenced by the philosophy of statistical hypothesis testing. A worthwhile alternative is to plan study size based on precision, for example by aiming to obtain a desired width of a confidence interval for the targeted effect. This article presents formulas for planning the size of an epidemiologic study based on the desired precision of the basic epidemiologic effect measures.

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