[R] ANOVA Permutation Test

Michael Dewey ||@t@ @end|ng |rom dewey@myzen@co@uk
Mon Sep 3 17:58:46 CEST 2018


Dear Juan

I do not use the package but if it does permutation tests it presumably 
uses random numbers and since you are not setting the seed you would get 
different values for each run.

Michael

On 03/09/2018 16:17, Juan Telleria Ruiz de Aguirre wrote:
> Dear R users,
> 
> I have the following Question related to Package lmPerm:
> 
> This package uses a modified version of aov() function, which uses
> Permutation Tests instead of Normal Theory Tests for fitting an Analysis of
> Variance (ANOVA) Model.
> 
> However, when I run the following code for a simple linear model:
> 
> library(lmPerm)
> 
> e$t_Downtime_per_Intervention_Successful %>%
>    aovp(
>      formula = `Downtime per Intervention[h]` ~ `Working Hours`,
>      data = .
>    ) %>%
>    summary()
> 
> I obtain different p-values for each run!
> 
> With a regular ANOVA Test, I obtain instead a constant F-statistic, but I
> do not fulfill the required Normality Assumptions.
> 
> So my questions are:
> 
> Would it still be possible use the regular aov() by generating permutations
> in advance (Obtaining therefore a Normal Distribution thanks to the Central
> Limit Theorem)? And applying the aov() function afterwards? Does it have
> sense?
> 
> 
> Or maybe this issue could be due to unbalanced classes? I also tried to
> weight observations based on proportions, but the function failed.
> 
> 
> Any alternative solution for performing a One-Way ANOVA Test over
> Non-Normal Data?
> 
> 
> Thank you.
> 
> Juan
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Michael
http://www.dewey.myzen.co.uk/home.html




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