A concrete type I/III Sum of square problem
More to the point, you are confusing multistratum AOV with single-stratuam AOV. For a good tutorial, see MASS4 (bibliographic information in the R FAQ). For unbalanced data we suggest you use lme() instead.
On Tue, 14 Feb 2006, WPhantom wrote:
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
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595