How is dispersion of the series different from the average of the series? What will be the effect of change of origin and change of scale on S.D. mean and variance series?

(a) Difference between dispersion of series and average of series : Averages of series in known as the measures of central tendency. An average indicates respresentative value of the series around which other value of the series tend to converage. So the average represents the series as a whole. In the other hand dispersion is the measure of the variationes of the items. It helps us in knowing about the composition of a series or the dispersal of values on the either side of the central tendency.

(b) Effect of change of origin and change of scale in the S.D. mean and variance : Change of origin i.e. any constant added or subtracted will have no effect on standard deviation but it will change the mean.

On the other hand change of scale (any constant multiplied or divided) will change the mean, standard deviation and variance.