# what is correlation???!!!!

#### haraharae

##### New Member
what is the meaning of correlation??????????

#### Dason

Cor(X, Y) = Cov(X, Y)/sqrt(Var(X)*Var(Y)) where Cov is the covariance function, Var is the variance function and sqrt is the square root.

#### Karabiner

##### TS Contributor
I beg to differ. The correct answer is

Cor(X, Y) = Cov(X, Y)/sqrt(Var(X)*Var(Y)) !!!!!!!!!!!!!! where Cov is the covariance function, Var is the variance function and sqrt is the square root!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

#### hlsmith

##### Omega Contributor
haraharae needs input!!!!!!!!!!!!!

#### fritz

##### New Member
Another formula: the correlation between X and Y is the average of the product of their standardized values, i.e., the average of {the number of standard deviations of X from its mean} times {the number standard deviations of Y from its mean}. (The population standard deviations must be used here.) It is also worth noting that the correlation is the slope coefficient in a regression of the standardized value of Y on the standardized value of X. See:
http://people.duke.edu/~rnau/regintro.htm#correlation or
http://people.duke.edu/~rnau/mathreg.htm#slopeintercept