:10a. Solution.  The deviations from the average are  -5, -1,
-1, 1, 1, 5.  The average of the square deviations is <p>

(25 + 1 + 1 + 1 + 1 + 25)/6  =  54/6  =  9 <p>

The SD is the square root of 9, or 3. <p>