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

[WPhantom]

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