Variation Series

a series of any numbers arranged in order of increasing value. For example, the variation series of the numbers 1, -3, 8, 2 takes the form -3, 1, 2, 8. The interval between the extreme members of a variation series is called the interval of variation, and the length of this interval is called the range. In mathematical statistics, the concept of variation series forms the basis of the theory of solutions of so-called nonparametric problems.