Planning Study Size Based on Precision Rather Than Power

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


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.

MeSH terms

  • Confidence Intervals
  • Humans
  • Probability
  • Research Design*
  • Sample Size*
  • Statistics as Topic