R help - Jan 2003 - Greenhouse-Geisser correction

Hi all,

I was wondering whether there are any packages that provide for the 
Greenhouse-Geisser correction, an adjustment used in univariate repeated 
measures when the sphericity assumption is violated (both numerator and 
denominator degrees of freedom are multiplied by GG-epsilon, and the 
significance of the F ratio is evaluated with the new degrees of freedom)? I 
have seen a few emails with the same question, to which nobody replied, but 
am hoping that maybe in the mean time somebody has tried to work this out.

Thanks much,
Heleen

That's a kludge.  You can analyse such models in a principled way using
either summary.manova or lme, both of which model the correlation in the 
`repeated measures' rather than wish it away.

Could you try to use a more informative subject?  Although I knew what the
correction was, I have never called it that.

On Mon, 27 Jan 2003, Heleen Slagter wrote:
> I was wondering whether there are any packages that provide for the 
> Greenhouse-Geisser correction, an adjustment used in univariate repeated 
> measures when the sphericity assumption is violated (both numerator and 
> denominator degrees of freedom are multiplied by GG-epsilon, and the 
> significance of the F ratio is evaluated with the new degrees of freedom)?
I
> have seen a few emails with the same question, to which nobody replied, but
> am hoping that maybe in the mean time somebody has tried to work this out.
-- 
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