Dear David I'd not recommend the tests (for normality, equal variances) as they are described on your second link (wikipedia).
I would use graphical tools such as Tukey-Anscombe Plot (residuals against fitted values), quantile (or normal) plot, leverage plot. see also ?plot.lm for some short descriptions of these plots in R. Best regards, Christoph Daniel Tahin writes: > Thanx for your answer. I don't have the book, but found something on > the web: > http://www.basic.northwestern.edu/statguidefiles/oneway_anova.html > and > http://en.wikipedia.org/wiki/Analysis_of_variance#Assumptions > > Seems to be the same on both of the sites :-) > Is this, that was meant? > > Thanx again, > Daniel > > > > > > 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 > > > > -------------------------------------------------------------- > > > > Credit and Surety PML study: visit our web page www.cs-pml.org > > > > -------------------------------------------------------------- > > Christoph Buser <[EMAIL PROTECTED]> > > Seminar fuer Statistik, LEO C13 > > ETH Zurich 8092 Zurich SWITZERLAND > > phone: x-41-44-632-4673 fax: 632-1228 > > http://stat.ethz.ch/~buser/ > > -------------------------------------------------------------- > > > > > > 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 > > > > > > ______________________________________________ > > > R-help@stat.math.ethz.ch 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. > ______________________________________________ R-help@stat.math.ethz.ch 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.
