title: Sample size in guidelines trials.
abstract: In clinical trials, the statistical concepts of significance and power are used in the determination of sample size for trials. The trialist must provide an estimate of standard deviation and a hypothetical population difference to be detected. This must be modified to deal with the designs encountered in guideline research. These are cluster randomized trials, because the patients of a single doctor or practice form a cluster. The trialist must be able to provide information about the effects of clustering, in the form of an intraclass correlation coefficient.
authors.affiliation: Department of Public Health Sciences, St George's Hospital Medical School, London, UK.
authors.forename: J M
authors.initials: JM
authors.lastname: Bland
mesh_terms: D005194:Family Practice; D006801:Humans; D017410:Practice Guidelines as Topic; D016032:Randomized Controlled Trials as Topic; D018401:Sample Size; D013223:Statistics as Topic