Anova - adjusted or sequential sums of squares?
On Wed, 20 Apr 2005, michael watson (IAH-C) wrote:
I guess what I want to know is if I use the type I sequential SS, as reported by R, on my factorial anova which is unbalanced, am I doing something horribly wrong? I think the answer is no.
Sort of. You really should test a hypothesis at a time. See Bill's examples in MASS.
I guess I could use drop1() to get from the type I to the type III in R...
Only if you respect marginality. The quote Doug gave is based on a longer paper available at http://www.stats.ox.ac.uk/pub/MASS3/Exegeses.pdf Do read it all.
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