A simple approximation for calculating sample sizes for detecting linear trend in proportions

Biometrics. 1987 Sep;43(3):701-5.


A simple approximate formula for sample sizes for detecting a linear trend in proportions is derived. The formulas for both the uncorrected and corrected Cochran-Armitage test are given. For two binomial proportions these reduce to those given by Casagrande, Pike, and Smith (1978, Biometrics 34, 483-486). Some numerical results of a power study for small sample sizes show that the nominal power corresponding to the approximate sample size is a reasonably good approximation to the actual power.

MeSH terms

  • Analysis of Variance
  • Animals
  • Carcinogens*
  • Neoplasms, Experimental / pathology*
  • Research Design*


  • Carcinogens