Exhibit 8-4
In order to estimate the average electric usage per month, a sample of 81 houses was selected, and the electric usage was determined. Assume a population standard deviation of 450-kilowatt hours.
-Refer to Exhibit 8-4. The standard error of the mean is
A)450
B)81
C)500
D)50

Question

Quizplus · Accepted Answer

The formula for standard error of the mean is:

standard error of the mean = population standard deviation / square root of sample size

Plugging in the given values, we get:

standard error of the mean = 450 / square root of 81

Simplifying, we get:

standard error of the mean = 450 / 9

standard error of the mean = 50

Therefore, the correct choice is D.

Exhibit 8-4 In Order to Estimate the Average Electric Usage Per Month