title: Sample size calculations for the design of health studies: a review of key concepts for non-statisticians.
abstract: Sample size calculations before conducting a health study or clinical trial are important to provide evidence that the proposed study is capable of detecting real associations between study factors. This review aims to clarify statistical issues related to the calculation of sample sizes and is illustrated with an example of a recent study design to improve health outcomes related to water and sewage in NSW Aboriginal communities. The effect of power, significance level and effect size on sample size are discussed. Calculations of sample sizes for individual-based studies are modified for more complex trial designs by multiplying individual-based estimates by an inflationary factor.
authors.affiliation: Centre for Epidemiology and Evidence, NSW Ministry of Health, Australia. amerr@doh.health.nsw.gov.au
authors.forename: Alistair
authors.initials: A
authors.lastname: Merrifield
authors.forename: Wayne
authors.initials: W
authors.lastname: Smith
mesh_terms: D002986:Clinical Trials as Topic; D003627:Data Interpretation, Statistical; D006304:Health Status; D006801:Humans; D011634:Public Health / Q000706:statistics & numerical data*; D012107:Research Design; D018401:Sample Size; D012722:Sewage; D018508:Water Purification; D014881:Water Supply
chemical_list: D012722:Sewage