' The figure shows scattering patterns of marbles thrown by three students A,B and C. In this game, the student who has the smallest scatter is the winner. In these examples, the degree of scattering ranges from A to C. In such a case, it is convenient if we have some numerical measure to indicate the degree of scattering. Then, think about it from various points of view, and show ways of indicating the degree of scattering by itemized statements. After that, think of the best answer for this problem.