I encounter a statistic problem about correlation.
I use R to test wether two variables are correlated or not.
(pearson correlation)
cor.test(x,y) give a p=5.87....
Because the x, y is not normal distributed (qqplot indicate that) I
also perform
(spearman rank correlation)
cor.test(x,y,method="spearman") give a very significant result p<10e-4
I don't know how to explain this. Will this result tell us that x, y
are correlated but not a linear one, and we can't
use the coefficient estimated by spearman rank correlation because its
interpretation is not quite clear.
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