Question

Omar recorded the number of hours he worked each week for a year. Below is a random sample that he took from his data.

13, 17, 9, 21


What is the standard deviation for the data?


Standard deviation: s = StartRoot StartFraction (x 1 minus x overbar) squared + (x 2 minus x overbar) squared + ellipsis + (x n minus x overbar) squared Over n minus 1 EndFraction EndRoot.


A.) 0

B.) 4

C) 2

D.) 26.7

Answer 1

Answer: B) 4

Explanation:

Using the formula

Standard deviation = √( (Σ ( x - π)²)/n)

To get the standard deviation, first we workout the Mean which is the simple average of the data set

n = 4

(13 + 17 + 9 + 21) / 4 = 60/4 = 15

Mean(x) = 15

Then (x-π)²

13 - 15 = (-2)² = 4

17 - 15 = (2)² = 4

9 - 15 = (-6)² = 36

21 - 15 = (6)² = 36

Σ ( x - π)² = (4 + 4 + 36 + 36) = 80

Standard deviation = √( (Σ ( x - π)²)/n

= √ (80/4)

=√20

= 4.47

= 4