Type II and III sum of squares (R and SPSS)
On Mar 22, 2012, at 13:29 , Helios de Rosario wrote:
M3$fattA <- as.factor(M3$fattA) Now, type III SS with Anova() only provides sensible results, if the factor contrasts are orthogonal, e.g. "contr.sum", "contr.poly", or "contr.helmert". This is not the default in R, so you should make it explicit: f5<-lm(cbind(b1,b2,b3)~fattA,data=M3, contrasts=list(fattA="contr.sum"))
Ah, thanks. I did suspect that contrast coding was involved, but nothing happened when I tried changing them. Of course, if one of the "factors" isn't.... Presumably, things also clear up if you code fattA as rep(c(-1,1),each=4).
Peter Dalgaard, Professor Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com