What is the standard deviation of the data set given below? 4, 7, 8, 9, 12

a.

b.

c. 8.5

d. 6.8

e. 2.5

f.

First we find the mean (average)

(4 + 7 + 8 + 9 + 12) / 5 = 40/5 = 8

now we subtract the mean (8) from every number in ur data ... then square it.

4 - 8 = - 4 ... - 4^2 = 16

7 - 8 = - 1 ... - 1^2 = 1

8 - 8 = 0 ... 0^2 = 0

9 - 8 = 1 ... 1^2 = 1

12 - 8 = 4 ... 4^2 = 16

now find the mean (average) of those numbers ...

(16 + 1 + 0 + 1 + 16) / 5 = 34/5 = 6.8 ... this is ur variance

the standard deviation is the square root of the variance

sqrt 6.8 = 2.6 < = = standard deviation