Dear Stefan, One place is my Applied Regression text (Sage, 1997 or 2008).
Regards, John ------------------------------ John Fox, Professor Department of Sociology McMaster University Hamilton, Ontario, Canada web: socserv.mcmaster.ca/jfox > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Stefan Uhmann > Sent: September-26-08 8:20 AM > To: r-help@r-project.org > Subject: Re: [R] Type I and Type III SS in anova > > Dear list, > > slightly OT: can you recommend me any sources where I can find more > about this Type I - II - III anova problem? It seems as my statistics > courses did not cover this issue, so I feel rather naive and have this > sort of feeling that some of my analyses might be complete nonsense. > > Regards, > Stefan > > John Fox schrieb, Am 26.09.2008 12:36: > > Dear Menelaos, > > > >> -----Original Message----- > >> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > > On > >> Behalf Of Menelaos Stavrinides > >> Sent: September-25-08 9:56 PM > >> To: r-help@r-project.org > >> Subject: [R] Type I and Type III SS in anova > >> > >> Hi all, > >> I have been trying to calculate Type III SS in R for an unbalanced two-way > >> anova. However, the Type III SS are lower for the first factor compared to > >> type I but higher for the second factor (see below). I have the impression > >> that Type III are always lower than Type I - is that right? > > > > No. > > > >> And a clarification about how to fit Type III SS. Fitting > > model<-aov(y~a*b) > >> in the base package and then loading car / changing contrasts / running > >> Anova(model,type=c("III")) gives different results compared to loading car > > / > >> changing contrasts / fitting model<-aov(y~a*b) / running > >> Anova(model,type=c("III")). However summary(model) gives the same results > > in > >> both cases. Is this how it is set up? > > > > If you use "type-III" tests in an unbalanced ANOVA, and want to test > > sensible hypotheses, you should use an orthogonal row-basis for the > effects, > > such as is provided by contr.helmert, contr.poly, or contr.sum, but not by > > the default contr.treatment. When you fit a model before changing the > > contrast type, contr.treatment is used. Changing the contrast type > > subsequent to that has no effect on a model that's already fit (how could > > it, unless, e.g., the model is updated?). Because the summary method for > aov > > objects reports "typei-I" (sequential) tests, the results are independent > of > > the contrast type. > > > > Regards, > > John > > > >>> local({pkg <- select.list(sort(.packages(all.available = TRUE))) > >> + if(nchar(pkg)) library(pkg, character.only=TRUE)}) > >>> options(contrasts=c("contr.helmert","contr.poly")) > >>> model2<-aov(tdrate~temp*sex) > >>> summary(model2) > >> Df Sum Sq Mean Sq F value Pr(>F) > >> temp 3 0.110137 0.036712 1005.6947 < 2e-16 *** > >> sex 1 0.000141 0.000141 3.8593 0.05095 . > >> temp:sex 3 0.000154 0.000051 1.4073 0.24206 > >> Residuals 187 0.006826 0.000037 > >> --- > >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 > >>> Anova(model2,type=c"III") > >> Error: unexpected string constant in "Anova(model2,type=c"III"" > >>> Anova(model2,type=c("III")) > >> Anova Table (Type III tests) > >> > >> Response: tdrate > >> Sum Sq Df F value Pr(>F) > >> (Intercept) 0.57549 1 15764.9249 < 2e-16 *** > >> temp 0.08571 3 782.6314 < 2e-16 *** > >> sex 0.00023 1 6.2851 0.01303 * > >> temp:sex 0.00015 3 1.4073 0.24206 > >> Residuals 0.00683 187 > >> --- > >> Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 > >> > >> -- > >> Menelaos Stavrinides > >> Ph.D. Candidate > >> Environmental Science, Policy and Management > >> 137 Mulford Hall MC #3114 > >> University of California > >> Berkeley, CA 94720-3114 USA > >> Tel: 510 717 5249 > >> > >> [[alternative HTML version deleted]] > >> > >> ______________________________________________ > >> R-help@r-project.org 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@r-project.org 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@r-project.org 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@r-project.org 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.
