find the standard deviation of the data set to the nearest tenth. (21,13,18,16,13,35,12,8,15).?

Question

a. 16.8
b. 7.8
c. 7.3
d. 5.7

(21,13,18,16,13,35,12,8,15)

Answer 1

The mean is 151/9.

(1/9)[(21-151/9)^2 + (13-151/9)^2 + (18-151/9)^2 + (16-151/9)^2 + (13-151/9)^2 + (35-151/9)^2 + (12-151/9)^2 + (8-151/9)^2 + (15-151/9)^2] =

(1/9)[(1444/81) + (1156/81) + (121/81) + (49/81) + (1156/81) + (26896/81) + (1849/81) + (6241/81) + (256/81)] =

(1/9)[39168/81] = 39168/729

√(39168/729) ≈ 7.3

The answer is c.