1. (a) Prove that the some of the squared deviations is least when taken from the mean.
(b) Dispersion is known as the average of the second order. Give reasons.
2. (a) Which measure of dispersion would be most useful for:
(i) a social worker,
(ii) an actuary.
(iii) A public relations man for industry, and
(iv) a spokesman for organised labour?
(b) What is coefficient of dispersion? What purpose does it serve?