Hi, Thanks for this information. Is there any way to force R to use Type-1 SS? I think most textbooks use this only.
Thanks and regards, On Wed, 7 Aug 2024 at 17:00, Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > > On 2024-08-07 6:06 a.m., Brian Smith wrote: > > Hi, > > > > I have performed ANOVA as below > > > > dat = data.frame( > > 'A' = c(-0.3960025, -0.3492880, -1.5893792, -1.4579074, -4.9214873, > > -0.8575018, -2.5551363, -0.9366557, -1.4307489, -0.3943704), > > 'B' = c(2,1,2,2,1,2,2,2,2,2), > > 'C' = c(0,1,1,1,1,1,1,0,1,1)) > > > > summary(aov(A ~ B * C, dat)) > > > > However now I also tried to calculate SSE for factor C > > > > Mean = sapply(split(dat, dat$C), function(x) mean(x$A)) > > N = sapply(split(dat, dat$C), function(x) dim(x)[1]) > > > > N[1] * (Mean[1] - mean(dat$A))^2 + N[2] * (Mean[2] - mean(dat$A))^2 > > #1.691 > > > > But in ANOVA table the sum-square for C is reported as 0.77. > > > > Could you please help how exactly this C = 0.77 is obtained from aov() > > Your design isn't balanced, so there are several ways to calculate the > SS for C. What you have calculated looks like the "Type I SS" in SAS > notation, if I remember correctly, assuming that C enters the model > before B. That's not what R uses; I think it is Type II SS. > > For some details about this, see > https://mcfromnz.wordpress.com/2011/03/02/anova-type-iiiiii-ss-explained/ > ______________________________________________ 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.
