ABSTRACT
Average alone cannot adequately describe a set of observations, unless all the observations are the same. It is necessary to describe the variability of dispersion of the observations. Also, in two or more distributions the central value may be the same, but still there can be wide disparities in the formation of the distribution. Measures of variation help us in studying this important characteristic of a distribution, that is the extent to which the items vary, from one another and from some central value.
