[R] permutation test assumption?

[Nordlund, Dan (DSHS/RDA)]

> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of João Fadista
> Sent: Tuesday, April 08, 2008 3:10 PM
> To: ONKELINX, Thierry; r-help at r-project.org
> Subject: Re: [R] permutation test assumption?
> 
> Dear Thierry,
>  
> Thanks for the reply. But as you may read in the paper 
> http://bioinformatics.oxfordjournals.org/cgi/content/abstract/
> 22/18/2244 when the sample sizes are not the same there may 
> be an increase in the Type I error rate.
>  
> Comments will be appreciated.
>  
> Best regards,
> João Fadista
>  
> 
> ________________________________
> 
> De: ONKELINX, Thierry [mailto:Thierry.ONKELINX at inbo.be]
> Enviada: ter 08-04-2008 15:27
> Para: João Fadista; r-help at r-project.org
> Assunto: RE: [R] permutation test assumption?
> 
> 
> 
> Dear João,
> 
> You can do permutation tests on an unbalanced design.
> 
> HTH,
> 
> Thierry
> 

João,

I haven't read the paper, but the abstract didn't mention different sample sizes as a problem.  Do the authors comment on sample size in the paper itself?  If so, what did they say?  If not, then why do you think sample size is a problem?

Dan 

Daniel J. Nordlund
Research and Data Analysis
Washington State Department of Social and Health Services
Olympia, WA  98504-5204