title: Statistics review 4: sample size calculations.
abstract: 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.
authors.affiliation: Medical Statistics, University of Bristol, Bristol, UK.
authors.forename: Elise
authors.initials: E
authors.lastname: Whitley
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ball
mesh_terms: D002986:Clinical Trials as Topic; D006801:Humans; D012107:Research Design; D012128:Respiratory Distress Syndrome / Q000628:therapy; D018401:Sample Size; D012772:Shock, Septic / Q000188:drug therapy; D013223:Statistics as Topic