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

[Prof Brian Ripley]

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)
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