[R] Problem with Kruskal–Wallis test

Michael Dewey li@t@ @ending from dewey@myzen@co@uk
Sat Dec 22 13:34:45 CET 2018

Dear Giuseppe

If I understand you correctly you have a very large sample size so it is 
not surprising that you get very small p-values. Eevn a scientifically 
uninteresting difference can become statistically significant with large 
samples. You probably need to define a metric for meaningful differences 
between groups and calculate a confidence interval for it.


On 21/12/2018 15:37, Giuseppe Cillis wrote:
> Dear all,
> I am a beginner with R (and also with the statistics) for which I hope to
> be clear.
> I should do this non-parametric test on data I extracted from maps.
> In practice I have a column that represents the landscape Dynamics of a
> certain time period (there are 3 dynamics, each of them marked by the
> number 1, 2 or 3) and the other column with the values of a topographic
> variable (for example the slope) . In all, there are more than 90,000 pairs
> of values.
> Going to do the test in R, for all the dynamics and for all the variables,
> I get out of the values of chi-square elevated (even in the order of
> thousands) and a p-value always <2.2e-16 .... why? Where can the error be? in
> the script or in the test approach?
> Thanks in advance
> 	[[alternative HTML version deleted]]
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