[R] ANOVA procedure on the sufficient statistics

Duncan Murdoch dmurdoch at pair.com
Thu Feb 19 17:36:40 CET 2004

On Thu, 19 Feb 2004 08:45:01 -0500, Michael Friendly
<friendly at yorku.ca> wrote :

>>You can apply the trick that Prof. Dalgaard recently posted in response to a
>>similar question (for one-way ANOVA).  For each cell, generate data as:
>>y <- cell.mean + cell.sd * scale(rnorm(cell.count))
>>Then generate the data frame to feed to aov.
>That will generate only approximately the same means and MSE, however.
>Larsen's procedure generates a weighted data set that gives the same 
>ANOVA table
>as the raw data, but requires that the weight= argument be used in aov().
>(weights are not supported in all related functions)

Are you sure about that?  I think the call to "scale()" makes them
come out identical.

In fact, the call to rnorm() is unnecessary; it would work just as
well with 

y <- cell.mean + cell.sd * scale(1:cell.count)

(unless I'm missing something...)


More information about the R-help mailing list