Question

: the variance of a series of numbers is the sum of the squares of their differences from the mean (average) of the numbers divided by the number of items in the series. variance is a common measure of risk. what is the variance of these investment returns? 10, 30, 20

Answer 1

The given data; 10,30,20
The mean will be (10+30+20)/3 = 20
Deviation from the mean will be; -10, 10, 0
Square of the deviations will be; 100, 100, 0 
The sum of the square of the deviations = 200
The variance will therefore be; sum of the square of deviations from the mean divided by the N (3)
 = 200/3 = 66.67
Thus; the variance = 66.67