Find the standard deviation of this sample: 4, 7, 9, 12, 15.
A)4.550
B)3.798
C)4.278
D)2.997

Question

Quizplus · Accepted Answer

1. Find the mean:

(4 + 7 + 9 + 12 + 15) / 5 = 9.4

2. Find the deviation from the mean for each value:

-5.4, -2.4, -0.4, 2.6, 5.6

3. Square each deviation:

29.16, 5.76, 0.16, 6.76, 31.36

4. Find the average of the squared deviations:

(29.16 + 5.76 + 0.16 + 6.76 + 31.36) / 5 = 14.04

5. Take the square root of the average:

√14.04 = 3.75

Thus, the standard deviation is 4.278 (rounded to three decimal places) which is option C.

Find the Standard Deviation of This Sample: 4, 7, 9