Which group exhibits the most variability

A. 2,2,3,11,12,12
B. 2,3,4,10,11,12
C. 2,4,6,8,10,12
D. 2,6,7,7,8,12

Please explain to me the answer Thanks so much :D

A.
mean = 7.
Sum of Squares = sum[(x-mean)^2]
= (2-7)^2 + ..... + (12-7)^2
= 132

B.
mean = 7, SSQ = 100

C.
mean = 7, SSQ = 70

D.
mean = 7, SSQ = 52

Hence, data set A has the most variability.

Usually, we use the dispersion measure, standard deviation, to calculate variability. The formula for standard deviation is:

(((Xi - mean of the data series) ^ 2)/ n) ^ 0.5

Xi = individual data point
n = number of data points in your data series

Alternatively, you can use an excel function stdevp function to do the calculation for you. Anyway, the answer is: "A".