The R Book by Crawley Michael J

Author:Crawley, Michael J.
Language: eng
Format: epub, pdf
ISBN: 9781118448960
Publisher: Wiley
Published: 2012-11-05T16:00:00+00:00

Here you see all the values that we calculated longhand. The error row is labelled Residuals. In the second and subsequent columns you see the degrees of freedom for treatment and error (2 and 27), the treatment and error sums of squares (99.2 and 315.5), the treatment mean square of 49.6, the error variance s2 = 11.685, the F ratio and the p value (labelled Pr(>F)). The single asterisk next to the p value indicates that the difference between the soil means is significant at 5% (but not at 1%, which would have merited two asterisks). Notice that R does not print the bottom row of the ANOVA table showing the total sum of squares and total degrees of freedom.

The next thing we would do is to check the assumptions of the aov model. This is done using plot like this (see p. 419):

par(mfrow=c(2,2))

plot(aov(yield∼soil))

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