[R] Posthoc tests for ANOVA

[Prof Brian Ripley]

On Wed, 23 Jan 2002 Jan_Svatos at eurotel.cz wrote:

> Dear List,
>
> are there post-hoc tests like Scheffe, LSD, etc. available after ANOVA test
> is performed with significant F-statistic?
> I have tried
> help.search("Scheffe"),
> but "No documentation found" (and I have most of packages installed).
> Probably there are such tests in R, and I am just searching badly...

This is usually known as `multiple comparisons', and there is not
much in R.  There are

1) Function Tukey in package Devore5
2) pairwise.t.test and friends in package ctest, including p.adjust.

but as S-PLUS users keep pointing out, multicomp there has much more.

> My second question is: Which test/method I should use for ANOVA-like test
> on 0-1 variables
> (leading to multiple binomial variables instead of Normal)?

Not sure I understand.  Anova is about a single response.  Perhaps you
mean logistic regression and the analysis of deviance?

Many of us would feel that testing is not important here: what is
important is to estimate sizes of effects and perhaps to select predictive
models.  Classical multiple comparisons deals with only a small part of
the selection effects, in particular ignores model choice.

-- 
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 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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