Which of the choices is the standard deviation of the sample shown here?

19, 20, 21, 22, 23

A. 2.5

B. 21

C. square root of 2.5

D. 2

E. square root of 2

Mean = (19 + 20 + 21 + 22 + 23) / 5 = 105/5 = 21

x x - mean (x - mean) ^2

19 - 2 4

20 - 1 1

21 0 0

22 1 1

23 2 4

Sum = 10

Standard deviation = sqrt (sum (x - mean) ^2 / n) = sqrt (10/5) = sqrt (2)