[R] A concrete type I/III Sum of square problem

From: WPhantom <wp1_at_tiscali.fr>
Date: Tue 14 Feb 2006 - 19:35:59 EST


Hi R-help members,

I have read a lot in the Archive about the "Type I" vs "Type III" sum of square. I think I have read confusing post so I want to have a clear idea of the problem.

Here is an example.
I have 3 groups of subjects of unequal sample size (G1 (n=7), G2
(n=7), G3 (n=4)).

for Each subject I have 4 measures corresponding to the crossing of 2 factor (A & B) of two levels each.

my dependant variable is X.

After reading a lot of tutorials on R I have tried the summary(aov(X~GROUP*A*B+Error(SUJECT/(A*B) )

This results are with "type I SS".

What's wrong with these results ? Should I use type III SS and, if so how to enter my design in Anova (car package, I still have not the J. Fox's book) ?
I have clearly not understood the difference between type I & III
(with the limits of each approach). A link to a good tutorial on
this topic will help me a lot.

Sylvain CLEMENT
"Neuropsychology & Auditory Cognition Team" Lille, FRANCE



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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Feb 14 19:43:00 2006

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