Sample Size for Independent Cohort Studies


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This function gives the minimum number of case subjects required to detect a true relative risk or experimental event rate with power POWER and two sided type I error probability ALPHA. This sample size is also given as a continuity-corrected value intended for use with corrected chi-square and Fisher's exact tests (Casagrande et al. 1978; Meinert 1986; Fleiss, 1981; Dupont, 1990).


Information required


Practical issues


Technical validation

The estimated sample size n is calculated as:

- where α = alpha, β = 1 - power, nc is the continuity corrected sample size and zp is the standard normal deviate for probability p. n is rounded up to the closest integer.