How can it be tested in R?
I would expect to do something like:
## From Venables and Ripley (2002) p.165. utils::data(npk, package="MASS") npk.aovE <- aov(yield ~ N*P*K + Error(block), npk) residuals(npk.aovE) qqnorm(residuals(npk.aov))
Which doesn't work, since "residuals" don't have a method (nor predict, for that matter) for the case of repeated measures anova.
So what should be done in this case?
Can the residuals simply be extracted from the same fit model without the Error term? I am not familiar enough with the literature to know if this is valid or not, thanks in advance for any suggestion.