Chapter 8.1, Problem 24E

To determine

The correct statement for the margin of error when confidence interval decreases

from 95% to 80% (a) 3%, because the same sample is used, (b) less than 3%, because the require

less confidence, (c) less than 3%, because the sample size is smaller, (d) greater than 3%, because we require less confidence, (e) greater than 3%, because the sample size is smaller.

Answer to Problem 24E

The correct option is (b) less than 3%, because we required less confidence.

Explanation of Solution

Given information:

Margin of error = 3%

Confidence interval = 90% to 80%

The confidence level is decreased from 95% to 80%. Thus, the confidence interval becomes less accurate and less wide.

Since decrease in confidence interval will decrease in the margin of error thus the margin of error will be less than 3%.

Hence, the correct option is (b).