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. At 95% confidence, the size of the margin of error is
A)1.96
B)50
C)98
D)42

Question

Quizplus · Accepted Answer

The margin of error is calculated using the formula: Margin of Error = Z * (σ/√n), where Z is the Z-score for the confidence level (1.96 for 95%), σ is the population standard deviation (450), and n is the sample size (81). Thus, Margin of Error = 1.96 * (450/√81) = 1.96 * 50 = 98.

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