Sample size formulas for estimating intraclass correlation coefficients with precision and assurance

Stat Med. 2012 Dec 20;31(29):3972-81. doi: 10.1002/sim.5466. Epub 2012 Jul 4.


The number of subjects required to estimate the intraclass correlation coefficient in a reliability study has usually been determined on the basis of the expected width of a confidence interval. However, this approach fails to explicitly consider the probability of achieving the desired interval width and may thus provide sample sizes that are too small to have adequate chance of achieving the desired precision. In this paper, we present a method that explicitly incorporates a prespecified probability of achieving the prespecified width or lower limit of a confidence interval. The resultant closed-form formulas are shown to be very accurate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Confidence Intervals
  • Humans
  • Models, Statistical*
  • Reproducibility of Results
  • Research Design
  • Sample Size*