title: A relative power table for nested matched case-control studies.
abstract: OBJECTIVE
  To calculate relative powers for nested case-control studies for different values of both relative risk and numbers of controls per case, given a fixed number of cases available for analysis.
  
  
  METHODS
  Algebraic and numerical methods.
  
  
  RESULTS
  In nested case-control studies, statistical power is a function of relative risk, rarity of exposure, number of case-control sets, and the number of controls per case.
  
  
  CONCLUSIONS
  The dictum that sufficient power will be obtained in a nested case-control study by selecting only four controls per case cannot be sustained. Appropriate numbers need to be calculated for specific studies.
authors.affiliation: Institute of Occupational Health, University of Birmingham, Edgbaston, UK.
authors.forename: D
authors.initials: D
authors.lastname: Pang
mesh_terms: D016022:Case-Control Studies; D006801:Humans; D015233:Models, Statistical; D018579:Patient Selection; D012016:Reference Values; D012107:Research Design