[R] pwr.2p2n.test when the ratio of n1/n2 is known

Daniel Brewer daniel.brewer at icr.ac.uk
Fri Oct 24 11:02:39 CEST 2008


I am trying to do a power calculation for a difference in proportions
test where I want to estimate the sample size required.  I know (well
estimate) that group one (n1) is 10% of the population and group 2 (n2)
is 90% of the population.  I know the effect size (h).  pwr.2p2n.test
only allows one variable to be left null whereas I would like both n1
and n2 to be determined where I know there relative proportions.  Any
ideas how to do this?  Is there a different function?



Daniel Brewer, Ph.D.

Institute of Cancer Research
Molecular Carcinogenesis
Email: daniel.brewer at icr.ac.uk

The Institute of Cancer Research: Royal Cancer Hospital, a charitable Company Limited by Guarantee, Registered in England under Company No. 534147 with its Registered Office at 123 Old Brompton Road, London SW7 3RP.

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