Correlation is a statistic that measures the degree to which two variables move in relation to each other. Correlation measures association, but does not tell you if x causes y or vice versa, or if the association is caused by some third (perhaps unseen) factor.

It ranges from -1.0 to +1.0. The closer r is to +1 or -1, the more closely the two variables are related.

+1.0 = Strong Correlation in same direction

-1.0  = Strong Correlation in opposite direction

0 = No relationship between the variables.