Review
Statistics review 4: Sample size calculations
1 Lecturer in Medical Statistics, University of Bristol, Bristol, UK
2 Lecturer in Intensive Care Medicine, St George's Hospital Medical School, London, UK
Critical Care 2002, 6:335-341 doi:10.1186/cc1521
Published: 10 May 2002Abstract
The present review introduces the notion of statistical power and the hazard of under-powered studies. The problem of how to calculate an ideal sample size is also discussed within the context of factors that affect power, and specific methods for the calculation of sample size are presented for two common scenarios, along with extensions to the simplest case.