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.If the sample mean is 1858 kWh, the 95% confidence interval estimate of the population mean is
A) 1760 to 1956 kWh.
B) 1729 to 1987 kWh.
C) 1758 to 1958 kWh.
D) 1776 to 1940 kWh.

Question

Quizplus · Accepted Answer

The correct answer is A because the 95% confidence interval is 1760 to 1956 kWh. This is calculated using the formula: sample mean +/- 1.96 * (population standard deviation / square root of sample size).

In Order to Estimate the Average Electric Usage Per Month