BFIRST, FIND THE MEAN OF THE RETURNS, THEN TAKE DIFFERENCES AND SQ...

First, find the mean of the returns, then take differences and square them, add them up, divide by n-1

(called the variance) and take the square root of the variance to find the standard deviation.

Example for A: 16 + 20 + 12 = 48/3 = 16% average return.

16 – 16 = 02 = 0

20 – 16 = 42 = 16

12 – 16 = (-4)2 = 16

0 + 16 + 16 = 32/(3-1) = 16.5 = 4.0%