R help - Aug 2007 - Sphericity test in R for repeated measures ANOVA

Hi,
Is there a way to do a sphericity test in R for repeated measures ANOVA
(using aov or lme)? I can't find anything about it in the help.
Thanks

Orou

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?mauchly.test also ?anova.mlm

Another approach would be to do a direct test of compound symmetry by
fitting models with and without that structure, and compare them via a
likelihood ratio test.

Simon.

On Mon, 2007-08-20 at 19:08 -1000, Orou Gaoue wrote:
> Hi,
> Is there a way to do a sphericity test in R for repeated measures ANOVA
> (using aov or lme)? I can't find anything about it in the help.
> Thanks
> 
> Orou
> 
> 	[[alternative HTML version deleted]]
> 
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Orou Gaoue wrote:
> Hi,
> Is there a way to do a sphericity test in R for repeated measures ANOVA
> (using aov or lme)? I can't find anything about it in the help.
> Thanks
>
> Orou
>   
There is for lm() with multivariate response (mauchly.test).

For lme(), you can compare models with a corSymm correlation structure 
to ones with corCompSymm. Thus is a similar test, but not quite the same.

For aov() it doesn't really make sense, partly because the 
"repeatedness" is  ambiguous in some models, partly because aov's 
internal algorithms rely strongly on orthogonality with respect to a 
particular covariance structure. If you relax assumptions, orthogonality 
no longer holds.