title: A simple approximation for calculating sample sizes for detecting linear trend in proportions.
abstract: 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.
authors: Mathematical Statistics and Applied Mathematics Section, National Cancer Institute, Bethesda, Maryland 20892.
authors: J M
authors: JM
authors: Nam
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002273:Carcinogens; D009374:Neoplasms, Experimental / Q000473:pathology*; D012107:Research Design
chemical_list: D002273:Carcinogens