On Mon, 2007-06-25 at 17:53 +1000, Simon Blomberg wrote: > If you use lme, you can fit a general correlation structure to the > within-subject data, and compare the fit to a model assuming > uncorrelated within-subjects errors. That should tell you whether your > data are ...
correlated... (damn email gremlins.) > Aren't the G-G and H-F corrections only approximate fixes? > Surely it is better to work with a model that actually fits your data, > rather than using ad hoc adjustments towards a model that doesn't quite > fit. But I'm no psychologist. :-) > > Cheers, > > Simon. > > On Mon, 2007-06-25 at 08:22 +0200, Peter Dalgaard wrote: > > DarrenWeber wrote: > > > I'm an experimental psychologist and when I run ANOVA analysis in > > > SPSS, I normally ask for a test of non-sphericity (Box's M-test). I > > > also ask for output of the corrections for non-sphericity, such as > > > Greenhouse-Geisser and Huhn-Feldt. These tests and correction factors > > > are commonly used in the journals for experimental and other > > > psychology reports. I have been switching from SPSS to R for over a > > > year now, but I realize now that I don't have the non-sphericity test > > > and correction factors. > > > > > This can be done using anova.mlm() and mauchly.test() which work on > > "mlm" objects, i.e., lm() output where the response is a matrix. There > > is no theory, to my knowledge, to support it for general aov() models, > > the catch being that you need to have a within-subject covariance matrix. > > > > ______________________________________________ > > [email protected] mailing list > > https://stat.ethz.ch/mailman/listinfo/r-help > > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > > and provide commented, minimal, self-contained, reproducible code. -- Simon Blomberg, BSc (Hons), PhD, MAppStat. Lecturer and Consultant Statistician Faculty of Biological and Chemical Sciences The University of Queensland St. Lucia Queensland 4072 Australia Room 320, Goddard Building (8) T: +61 7 3365 2506 email: S.Blomberg1_at_uq.edu.au The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. - John Tukey. ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
