I have made a correlation between group A and B and the pearsson coefficient constant, r, is at 0.97. The values are expression levels and hence they are non-parametric. I wonder how can i calculate the p-value of this correlation between group A and B? I know how to calculate the p-value for the difference between group A and B, but not for the correlation between group A and B.

 

 

Thanks for any inputs!

Let x = tanh-1® ie x = 0.5*ln ((1+r)/(1-r))

 

x should be approximately normally distributed with mean 0 and variance 1/(n-3). This will allow you to work out p using z tables

This is called a Fisher transformation

 

Alternatively r*sqrt(n-2) / sqrt(1-r^2) should be distributed as a t distribution with n-2 degrees of freedom. Use t tables for p value