title: Sample size calculations for pilot randomized trials: a confidence interval approach.
abstract: OBJECTIVE
  To describe a method using confidence intervals (CIs) to estimate the sample size for a pilot randomized trial.
  
  
  METHODS
  Using one-sided CIs and the estimated effect size that would be sought in a large trial, we calculated the sample size needed for pilot trials.
  
  
  RESULTS
  Using an 80% one-sided CI, we estimated that a pilot trial should have at least 9% of the sample size of the main planned trial.
  
  
  CONCLUSIONS
  Using the estimated effect size difference for the main trial and using a one-sided CI, this allows us to calculate a sample size for a pilot trial, which will make its results more useful than at present.
authors.affiliation: York Trials Unit, Department of Health Sciences, University of York, Heslington, York YO10 5DD, UK.
authors.forename: Kim
authors.initials: K
authors.lastname: Cocks
authors.forename: David J
authors.initials: DJ
authors.lastname: Torgerson
mesh_terms: D016001:Confidence Intervals; D019317:Evidence-Based Medicine / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D010865:Pilot Projects; D017410:Practice Guidelines as Topic / Q000592:standards*; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D018401:Sample Size; D013223:Statistics as Topic; D006113:United Kingdom