mean-square deviation

mean-square deviation

[′mēn ′skwer dē·vē′ā·shən] (statistics) A measure of the extent to which a collection v1, v2, …, vn of numbers is unequal; it is given by the expression (1/ n)[(v1- v̄)2+ ⋯ + (vn - v̄)2], where v̄ is the mean of the numbers.