# [R] Estimated Effects Not Balanced

Justin Thong justinthong93 at gmail.com
Tue Aug 23 13:46:26 CEST 2016

```Hi,

Thanks Richard,

That was me playing with too many examples and having too many variables
just lying around. Thanks for the tip though.

On 22 August 2016 at 23:32, Bert Gunter <bgunter.4567 at gmail.com> wrote:

> Thanks, Rich. I didn't notice that!
>
> -- Bert
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along
> and sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
> On Mon, Aug 22, 2016 at 1:43 PM, Richard M. Heiberger <rmh at temple.edu>
> wrote:
> > The problem is that you have 12 observations and 1+2+10=13 degrees of
> freedom.
> > There should be 1 + 2 + 8 = 11 degrees of freedom.
> > Probably one of your variables is masked by something else in you
> workspace.
> > Protect yourself by using a data.frame
> >
> >> tmp <- data.frame(A=factor(c(1,1,1,1,1,1,2,2,2,2,2,2)),
> > + B=factor(c(1,1,2,2,3,3,1,1,2,2,3,3)),
> > + y=rnorm(12))
> >> mod <- aov(y ~ A+B, data=tmp)
> >> summary(mod)
> >             Df Sum Sq Mean Sq F value Pr(>F)
> > A            1  1.553   1.553   1.334  0.281
> > B            2  3.158   1.579   1.357  0.311
> > Residuals    8  9.311   1.164
> >
> > On Mon, Aug 22, 2016 at 11:15 AM, Justin Thong <justinthong93 at gmail.com>
> wrote:
> >> Something does not make sense in R. It has to do with the question of
> >> balance and unbalance.
> >>
> >> *A<-factor(c(1,1,1,1,1,1,2,2,2,2,2,2))*
> >> *B<-factor(c(1,1,2,2,3,3,1,1,2,2,3,3))*
> >> *y<-rnorm(12)*
> >> *mod<-aov(y~A+B)*
> >>
> >> I was under the impression that the design is balanced ie order does not
> >> effect the sums of squares. However, when I compute the anova R reports
> >> that the Estimated Effects are Unbalanced. I thought that when all
> >> combinations of levels of A and B have equal replications then the
> design
> >> is called balanced. But, R tends to think that when not all levels of A
> and
> >> levels of B have equal replication, then the "Estimated Effects are
> >> unbalanced".... Is this the same as the design being unbalanced? Because
> >> for the example below, where the error occured, the order does not
> matter
> >> (which make me think that the design is balanced).
> >>
> >>
> >> *Call:*
> >> *   aov(formula = y ~ A + B)*
> >>
> >> *Terms:*
> >> *                        A         B Residuals*
> >> *Sum of Squares   0.872572  0.025604 16.805706*
> >> *Deg. of Freedom         1         2        10*
> >>
> >> *Residual standard error: 1.296368*
> >> *Estimated effects may be unbalanced*
> >> --
> >> Yours sincerely,
> >> Justin
> >>
> >> *I check my email at 9AM and 4PM everyday*
> >> *If you have an EMERGENCY, contact me at +447938674419(UK) or
> >> +60125056192(Malaysia)*
> >>
> >>         [[alternative HTML version deleted]]
> >>
> >> ______________________________________________
> >> R-help at 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.
> >
> > ______________________________________________
> > R-help at 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.
>

--
Yours sincerely,
Justin

*I check my email at 9AM and 4PM everyday*
*If you have an EMERGENCY, contact me at +447938674419(UK) or
+60125056192(Malaysia)*

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```

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