Re: [R] multcomp: contrasts for count data

2009-06-15 Thread Julien Gagneur
Peter Westfall has answered me giving useful links. Here is the exchange: thanks for your quick answer and the refs. My misconception was that i treated the p-values as if they were non adjusted p-values. Discreteness was a minor problem. The p-values look much more uniform once I test on

[R] multcomp: contrasts for count data

2009-06-15 Thread Julien Gagneur
Hi, I would like to derive p-values for pair-wise comparison (Tukey's) of effects when the response is a count. I am trying a test case where y ~ Po( lambda(x) ). x has three levels : A, B and C with lambda(x) = 10, 20 and 20 respectively. Hence, p-values for the contrast C - B should distr