function [d,r]=Cohen(M1,SD1,M2,SD2)
%Calculate the value of Cohen's d and the effect-size correlation, r, using the means and standard deviations of two groups.
%M1,SD1 represent mean and standard deviation of Group 1
%M2,SD2 represent mean and standard deviation of Group 2
%ref:http://www.uccs.edu/~lbecker/
o = sqrt((SD1^2+SD2^2)/2);
d = (M1-M2)/o;
r = d/sqrt(d^2+4);