RE: [R] Anova - adjusted or sequential sums of squares?

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Thu 21 Apr 2005 - 01:35:21 EST

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@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

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Received on Thu Apr 21 02:24:21 2005

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