Hello,

Does anyone know which method from Newcombe (1998)* is implemented in prop.test for comparing two proportions?
I would guess it is the method based on the Wilson score (for single proportion), with and without continuity correction  for prop.test(..., correct=FALSE) and prop.test(..., correct=TRUE). These methods would correspond to no. 10 and 11 tested in Newcombe, respectively. Can someone confirm this? If not, which other methods are implemented by prop.test?

* Newcombe R.G. (1998) Two-Sided Confidence Intervals for the Single Proportion: Comparison of Seven Methods.  Statistics in Medicine  *17*, 857-872.

There is also the function ci.pd() from the R-package Epi, which should implement method no. 10 from Newcombe. However, prop.test(..., correct=FALSE) and ci.pd do not give the same result if I do the following:

successes <- c(21, 41)
total <- c(345, 345)
prop.test(successes, total, correct=FALSE)
library(Epi)
ci.pd(matrix(c(successes, total-successes),ncol=2, byrow=TRUE))

Can someone explain why?

Best wishes
Stefanie von Felten


Stefanie von Felten, PhD
Statistician
Clinical Trial Unit, CTU
University Hospital Basel
Schanzenstrasse 55
CH-4031 Basel

Phone: ++41(0)61 556 54 98

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