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
Waldweg 26
D-37073 Goettingen
Germany
phone +49 (0)551 39 8807
fax +49 (0)551 39 8806
Homepage http://www.gwdg.de/~cscherb1
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