[R] Type II and III sums of squares with Error in AOV

[Peter Dalgaard]

Prof Brian Ripley <ripley at stats.ox.ac.uk> writes:

> A multistratum aov() fit is just a list of aov() fits, so you can apply 
> functions such as Anova to the individual strata.
> 
> However, why do you want types II and III sums of squares?  It is usual 
> to do this type of analysis only with balanced designs.  In the cases I 
> can envisage that these make any sense, they are the same as type I
> (and in cases with only one treatment effect, they always are).


I was about to make a similar comment. A possible exception is ANCOVA
where you likely want to test both the within-stratum effect of a
covariate and the effect of design factors adjusted for the covariate.

 
> On Tue, 8 Nov 2005, Jarrett Byrnes wrote:
> 
> > I've recently run into the problem of using aov with nested factors,
> > and wanting to get the type II and III sums of squares.  Normally Anova
> > from the car package would do fine, but it doesn't like having an Error
> > included, so
> >
> > my.aov <-aov(Response ~ Treatment + Error(Treatment:Replicate))
> > Anova(my.aov, type="II")
> >
> > yields
> >
> > Error in Anova(nested.anova) : no applicable method for "Anova"
> >
> > And lm does not take Error as an argument.
> 
> Nor does log()!  Is that relevant?
> 
> > Error in eval(expr, envir, enclos) : couldn't find function "Error"
> >
> > Is there a way to get these additional types of sums of squares when
> > Error is included in an aov model?
> 
> Have you read the reference on the aov help page?  That might be a good 
> step to deepening your understanding of what Error() does.
> 
> -- 
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
> 
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-- 
   O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
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