Message-ID: <Pine.LNX.4.61.0504201630420.32678@gannet.stats>
Date: 2005-04-20T15:35:21Z
From: Brian Ripley
Subject: Anova - adjusted or sequential sums of squares?
In-Reply-To: <8975119BCD0AC5419D61A9CF1A923E950121BB2D@iahce2knas1.iah.bbsrc.reserved>
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