[R] Randomization tests, grouped data

Tom Backer Johnsen backer at psych.uib.no
Fri Jan 11 18:57:41 CET 2008

Tom Backer Johnsen wrote:
> The other day I was looking into one of the classics in resampling, 
> Eugene Edgington's "Randomization Tests".  This type of test is simple 
> to do in R with things like a simple correlation, the sample () 
> function is perfect for the purpose.
> However, things are more complex if you have grouped data, like a 
> one-way ANOVA.  The reason is that you have to avoid the consideration 
> of what Edgington calls "mirror samples", shuffles that only move data 
> within the groups.  After all, one only wants to consider changes 
> bewteen groups.  In that case (I think) the sample () function is too 
> general.
> Are there something that can handle this in R?

After a few hours thinking on and off about the problem, I suspect 
that the question may be stupid or silly (or both).  If that is the 
case, I would very much like to know why.



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