R usesType I sequential SS, not the default Type III marginal SS reported by SPSS. There is a good blog post explaining this difference along with some interesting comments -- http://myowelt.blogspot.com/2008/05/obtaining-same-anova-results-in-r-as-in.html
Best Wishes, Martin H. Teicher Dept of Psychiatry McLean Hospital / Harvard Medical School Belmont MA 02478 On Aug 13, 2010, at 10:32 PM, Ben Bolker wrote: > Leo Vorthoren <L.Vorthoren <at> nioo.knaw.nl> writes: > >> I have been using generalized linear models in SPSS 18, in order to build >> models and to calculate the P values. When I was building models in Excel >> (using the intercept and Bs from SPSS), I noticed that the graphs differed >> from my expectations. When I ran the dataset again in R, I got totally >> different outcomes for both the P values as well as the Bs and the >> intercepts. The outcomes of R seem much more likely to be the correct ones, >> but I really cannot explain the differences. > > I appreciate/assume that you're asking on the off chance that someone > else has tried something very similar and gone to the trouble of figuring > out the differences between R's and SPSS's default setup, but you're > unlikely to get an answer without more detailed information. > > My best guess is that SPSS and R are using different contrasts > and/or different baseline levels. R uses treatment contrasts by default, > and assumes that the first (alphabetical) level of a factor is the > baseline level. > > It's conceivable that you have a dataset where the results are > numerically unstable and sensitive to small details in the algorithms > used. > > ______________________________________________ > 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.
