Unmatched Case/Control Studies

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Choose which calculation you desire, enter the relevant population values (as decimal fractions) for p0 (exposure in the controls) and RR (relative risk of disease associated with exposure) and, if calculating power, a sample size (assumed the same for each sample). You may also modify α (type I error rate) and the power, if relevant. After making your entries, hit the calculate button at the bottom.

  • Calculate Sample Size (for specified Power)
  • Calculate Power (for specified Sample Size)
  • Enter a value for p0:
    Enter a value for RR:
  • 1 Sided Test
  • 2 Sided Test
  • Enter a value for α (default is .05):
    Enter a value for desired power (default is .80):
    The sample size (for cases and controls, separately) is:


    Reference: The calculations are the same as in Comparing Proportions for Two Independent Samples setting p1=p0 and p2= p0*RR/(1 + p0*(RR - 1)). See Schesselman, J. (1982), Case Control Studies, p. 145


    Rollin Brant
    Email me at: rollin@stat.ubc.ca