First find the mean This is 162.
Then work out deviations from the mean:-
= -27,-27,-20,-12,6,11,16,22,31
Square these values:- = 729,729,400,144,36,121,256,484,961
Add these up and divide the total by the number of values (9)
= 3860 / 9 = 428.888
Population standard deviation = square root of 428.888 = 20.71 to nearest hundredth (answer)