Dear Michael and Michael, I took a quick look at the Statistica website, and their definition of "types" of sums of squares doesn't appear to be the same as the common definition, which originated with SAS. As I read their materials, what they call "Type VI" sums of squares would correspond to the "Type III" tests provided by Anova() in the car package by setting type=3.
As well, the reference to "sigma-restricted coding" in the Statistica documentation corresponds to contrasts provided by contr.sum() in R. This is important for Type III tests because it produces a row-basis for the model matrix with orthogonal effects. One way to do this is via options(contrasts=c("contr.sum", "contr.poly")). See ?Anova for more information. I hope this helps, John ----------------------------- John Fox, Professor McMaster University Hamilton, Ontario Canada L8S 4M4 Web: socserv.mcmaster.ca/jfox > -----Original Message----- > From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Michael > Friendly > Sent: May 20, 2016 8:50 AM > To: michael.eisenr...@agroscope.admin.ch; r-help@r-project.org > Subject: Re: [R] Change sum of squares type for ANOVA > > Use car::Anova() for type II and type III sums of squares and F-tests. > The sequential type I tests computed by anova() are rarely sensible > > On 5/20/2016 3:11 AM, michael.eisenr...@agroscope.admin.ch wrote: > > Dear R-list members, > > > > I compared my statistics with my supervisor yesterday. He is using > STATISTICA, I am using R. We both loaded the same data-file and did a two-way > ANOVA with treatment and trial as factors; treatment means were then > compared to the untreated control using Dunnett's test. Surprisingly, we got > different values, especially the F values differed. In the following > Dunnett's test, > some treatments were significant in R, but not in STATISTICA. We checked the > basic settings of the programs and found out, that STATISTICA is using "sigma- > restricted parametrization" and "type VI sum of squares" for the calculations, > but so far, I could not find any information about the sum of squares type, > which is applied in R. Is it possible, that these settings are the reason for > the > different values we got? And how can I change in R these settings? > > > > Here the code I used: > > bt_assay_devtime_Model <- > > aov(developmenttime~treatment+run+treatment*run, data=bt_assay) > > summary(bt_assay_devtime_Model) > > postHocs_bt_assay_devtime <- glht(bt_assay_devtime_Model, > > linfct=mcp(treatment="Dunnett"), base=1) > > summary(postHocs_bt_assay_devtime) > > confint(postHocs_bt_assay_devtime) > > > > Thanks a lot for your help! > > Simone > > > > Eisenring Michael, Msc. > > PhD Student > > > > Federal Department of Economic Affairs, Education and Research EAER > > Institute of Sustainability Sciences ISS Biosafety > > > > Reckenholzstrasse 191, CH-8046 Z rich > > Tel. +41 44 37 77181 > > Fax +41 44 37 77201 > > michael.eisenr...@agroscope.admin.ch<mailto:michael.eisenring@agroscop > > e.admin.ch> www.agroscope.ch<http://www.agroscope.ch/> > > > > > > [[alternative HTML version deleted]] > > > > > > > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > 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 -- To UNSUBSCRIBE and more, see 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.