In order to estimate the average electric usage per month, a sample of 64 houses was selected and the electric usage was determined. Assume a population standard deviation of 320 kilowatt-hours. The standard error of the mean is
A) 320.
B) 64.
C) 400.
D) 40.

Question

Quizplus · Accepted Answer

The formula for standard error of the mean is:
Standard Error = (Population Standard Deviation) / sqrt(sample size)
Plugging in the values given,
Standard Error = 320 / sqrt(64) = 40. Therefore, the answer is D.

In Order to Estimate the Average Electric Usage Per Month