[R] Preconditions for a variance analysis

[Christoph Buser]

Dear David

Yes. There are assumptions that should be verified in an
analysis of variance. Without checking them, the results are not
reliable. 
I'd recommend e.g.

Robert O. Kuehl, Design of Experiments: Statistical Principles
  of Research Design and Analysis, Duxbury Press, 2000

You will find a chapter about assumptions and how to check them
by residual analysis,

And also

W. N. Venables and B. D. Ripley, Modern Applied Statistics 
  with S, Springer-Verlag, New York, 2002

in which you find residual analysis and how to obtain it in R.

Best regards,

Christoph

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Christoph Buser <buser at stat.math.ethz.ch>
Seminar fuer Statistik, LEO C13
ETH Zurich	8092 Zurich	 SWITZERLAND
phone: x-41-44-632-4673		fax: 632-1228
http://stat.ethz.ch/~buser/
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Daniel Tahin writes:
 > Hello everbody,
 > 
 > i'm currently using the anova()-test for a small data.frame of 40 
 > rows and 2 columns. It works well, but is there any preconditions for 
 > a valid variance analysis, that i should consider?
 > 
 > Thank you for your answer,
 > Daniel
 > 
 > ______________________________________________
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 > 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.