Carsten Jaeger wrote: > Hello, > > is it possible to obtain type III sums of squares for a nested model as > in the following: > > lmod <- lm(resp ~ A * B + (C %in% A), mydata)) > > I have tried > > library(car) > Anova(lmod, type="III") > > but this gives me an error (and I also understand from the documentation > of Anova as well as from a previous request > (http://finzi.psych.upenn.edu/R/Rhelp02a/archive/64477.html) that it is > not possible to specify nested models with car's Anova). > > anova(lmod) works, of course. > > My data (given below) is balanced so I expect the results to be similar > for both type I and type III sums of squares. But are they *exactly* the > same? The editor of the journal which I'm sending my manuscript to > requests what he calls "conventional" type III tests and I'm not sure if > > can convince him to accept my type I analysis. In balanced designs, type I-IV SSD's are all identical. However, I don't think the model does what I think you think it does.
Notice that "nesting" is used with two diferent meanings, in R it would be that the codings of C only makes sense within levels of A - e.g. if they were numbered 1:3 within each group, but with C==1 when A==1 having nothing to do with C==1 when A==2. SAS does something. er. else... What I think you want is a model where C is a random terms so that main effects of A can be tested, like in > summary(aov(resp ~ A * B + Error(C), dd)) Error: C Df Sum Sq Mean Sq F value Pr(>F) A 2 33.123 16.562 0.4981 0.6308 Residuals 6 199.501 33.250 Error: Within Df Sum Sq Mean Sq F value Pr(>F) B 1 915.21 915.21 83.7846 9.57e-05 *** A:B 2 16.13 8.07 0.7384 0.5168 Residuals 6 65.54 10.92 --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 (This is essentially the same structure as Martin Bleichner had earlier today, also @web.de. What is this? an epidemic? ;-)) -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ 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.