The variance of a list is the square of the standard deviation of the list, that is, the average of the squares of the deviations of the numbers in the list from their mean. The variance of a random variable X, Var(X), is the expected value of the squared difference between the variable and its expected value: Var(X) = E((X − E(X))²). The variance of a random variable is the square of the standard error (SE) of the variable.