R help - Jul 2008 - Three contrast matrices on the same linear model

Dear R users,

Suppose I want to look at three different types of contrasts after fitting a
linear model:

P1=contr.treatment(7)
P2=contr.helmert(7)
P3=contr.sdif(7) #from library(MASS)

contrasts(A)=P1
model1=aov(y~A)
summary(model1)

contrasts(A)=P2
model2=aov(y~A)
summary(model2)

contrasts(A)=P3
model3=aov(y~A)
summary(model3)

How do I have to adjust the P values for the number of comparisons made? In each
case, all
comparisons made are orthogonal, but because I use three contrast matrices, I
thought I would need
to work at alpha=0.05/3 or so. Any ideas?

Thanks and best wishes
Christoph


(using R 2.7.1 on Windows XP)







-- 
Dr. rer.nat. Christoph Scherber
University of Goettingen
DNPW, Agroecology
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