[R] repeated measures: Greenhouse-Geisser correction
ripley at stats.ox.ac.uk
Tue Jan 28 08:23:04 CET 2003
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
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