Sample size calculation for poisson endpoint using the exact distribution of difference between two poisson random variables


Journal Article

We propose a method that compares Poisson distributed outcomes. Our method uses the exact distribution of the difference between two Poisson variables to calculate the sample size required to detect a given difference with prespecified power. When the true difference between the two Poisson rates is more than 1.2 units, the number of subjects and events needed at the desired power and Type I error rate is 5-10% less than that computed by simulation based on the normal approximation method. The normal approximation method is more comparable to the exact sample size method when the difference between the rates is less than 1.2 units. The proposed method is more intuitive, efficient, and less subjective than the normal approximation method. A simple code is developed in R to estimate the sample size and critical values. © American Statistical Association Statistics in Biopharmaceutical Research.

Full Text

Duke Authors

Cited Authors

  • Menon, S; Massaro, J; Lewis, J; Pencina, M; Wang, YC; Lavin, P

Published Date

  • December 1, 2011

Published In

Volume / Issue

  • 3 / 3

Start / End Page

  • 497 - 504

Electronic International Standard Serial Number (EISSN)

  • 1946-6315

Digital Object Identifier (DOI)

  • 10.1198/sbr.2011.10015

Citation Source

  • Scopus