Covariation
Covariance or correlational moment of random variables - in probability theory and mathematical statistics, a measure of the dependence of two random variables.
In probability theory and statistics, covariance is a measure of the joint variability of two random variables. If larger values of one variable predominantly correspond to larger values of the other variable, and the same holds true for smaller values (i.e., the variables tend to have the same directionality) - the covariance is positive. With negative covariance, large values of one variable predominantly correspond to smaller values of the other and vice versa (i.e., the variables tend to have opposite directionality). The magnitude of covariance is harder to interpret because it is not normalized and therefore depends on the magnitude of the variables. The normalized version of covariance - the correlation coefficient - indicates the strength of the linear dependence by its magnitude.
