# PS2.3 -- on covariance and corr. coeff. - Section 2.5
open data2-2 
genr x = colgpa
genr y = hsgpa
genr n = $nobs
# mean of colgpa 			
genr xbar = mean(x)
# s.d. of colgpa 			
genr sx = sd(x)
# mean of hsgpa 			
genr ybar = mean(y)
# s.d. of hsgpa 			
genr sy = sd(y)
# cross product of deviation from mean 	
genr sxy = (x-xbar)*(y-ybar)
# compute covariance 		
genr covxy = sum(sxy)/(n-1)
# compute correlation coefficient 	
genr corxy = covxy/(sx*sy)
# reset sample range 		
smpl 1 1
# print values 		
print xbar sx ybar sy covxy corxy 
# reset sample range                 
smpl 1 427
# same with the corr command 	
corr x y 
# summary statistics                 
summary x y