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Power Calculations for Matched Case-Control Studies

William D. Dupont
Biometrics
Vol. 44, No. 4 (Dec., 1988), pp. 1157-1168
DOI: 10.2307/2531743
Stable URL: http://www.jstor.org/stable/2531743
Page Count: 12
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Power Calculations for Matched Case-Control Studies
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Abstract

Power calculations are derived for matched case-control studies in terms of the probability p0 of exposure among the control patients, the correlation coefficient φ for exposure between matched case and control patients, and the odds ratio ψ for exposure in case and control patients. For given Type I and Type II error probabilities α and β, the odds ratio that can be detected with a given sample size is derived as well as the sample size needed to detect a specified value of the odds ratio. Graphs are presented for paired designs that show the relationship between sample size and power for α = .05, β = .2, and different values of p0, φ, and ψ. The sample size needed for designs involving M matched control patients can be derived from these graphs by means of a simple equation. These results quantify the loss of power associated with increasing correlation between the exposure status of matched case and control patients. Sample size requirements are also greatly increased for values of p0 near 0 or 1. The relationship between sample size, ψ, φ, and p0 is discussed and illustrated by examples.

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