R help - Mar 2007 - Sphericity and post-hoc analysis in a repeated-measure ANOVA

Does anyone have any suggestions for how to test for violation of the  
sphericity assumption and apply the Huynh-Feldt correction to a  
repeated-measure model?  My model follows the format below:
	
		Rep.anova=aov(Y~X1*X2+Error(Subject/(X1*X2),data=DataFile))

I've already looked at the explanations aov() and Error() in Baron's  
“Notes on the use of R for psychology experiments and  
questionnaires,” which seems like a logical place for this   
information, but I didn't see anything.  Along a similar line, I'm  
also wondering if anyone has suggestions for how to implement post- 
hoc analyses on X1, after finding a significant main effect and no  
X1:X2 interaction, given that X1 has three levels and each subject in  
the analysis has data associated with each level.  Thank-you in  
advance for your suggestions.


Kyle H. Ambert
Graduate Student, Dept. Behavioral Neuroscience
Oregon Health & Science University
ambertk@ohsu.edu
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