[R] ANOVA in Randomized-complete blocks design
Simon Blomberg
blomsp at ozemail.com.au
Fri Nov 3 03:22:05 CET 2006
You have mis-transcribed the data:
Series Genotype Weight
1 pb 0.986
3 bb 0.829
anova(aov(weight ~ series + genotype, data=dat))
gives the correct results when compared to S&R.
Cheers,
Simon.
January Weiner wrote:
> Dear all,
>
> I am trying to repeat an example from Sokal and Rohlfs "Biometry" --
> Box 11.4, example of a randomized-complete-blocks experiment.
>
> The data is fairly simple:
>
> series genotype weight
> 1 pp 0.958
> 1 pb 0.985
> 1 bb 0.925
> 2 pp 0.971
> 2 pb 1.051
> 2 bb 0.952
> 3 pp 0.927
> 3 pb 0.891
> 3 bb 0.892
> 4 pp 0.971
> 4 pb 1.010
> 4 bb 0.955
>
> The model used for ANOVA in the book is
>
> Y_{ij} = \mu + \alpha_i + B_i + [(\alpha B)_{ij}] + \epsilon_{ij}
>
> (I am not quite confident how to represent this model in R, see below)
>
> The ANOVA table from S&R looks like this:
>
> MSB series 3 0.021 0.007 10.23 **
> MSA genotypes 2 0.010 0.005 6.97 *
> MSE error 6 0.004 0.001
>
> In R, I am using the following model (is this correct?)
>
> aov.ob = aov( genotype ~ genotype + series )
>
> However, my results are
>
> Df Sum Sq Mean Sq F value Pr(>F)
> series 3 0.0135867 0.0045289 6.6360 0.02469 *
> genotype 2 0.0056732 0.0028366 4.1563 0.07367 .
> Residuals 6 0.0040948 0.0006825
>
> What am I doing wrong?
>
> Regards,
> January
>
> --
>
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>
>
--
Simon Blomberg, B.Sc.(Hons.), Ph.D, M.App.Stat.
Centre for Resource and Environmental Studies
The Australian National University
Canberra ACT 0200
Australia
T: +61 2 6125 7800 email: Simon.Blomberg_at_anu.edu.au
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The combination of some data and an aching desire for
an answer does not ensure that a reasonable answer
can be extracted from a given body of data.
- John Tukey.
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