A 90% confidence interval for the average salary of all CEOs in the electronics industry was constructed using the results of a random survey of 45 CEOs. The interval was ($133,306, $150,733).
To make more useful inferences from the data, it is desired to reduce the width of the confidence interval. Which of the following will result in a reduced interval width?
A) Decrease the sample size and increase the confidence level.
B) Increase the sample size and decrease the confidence level.
C) Increase the sample size and increase the confidence level.
D) Decrease the sample size and decrease the confidence level.

Question

Quizplus · Accepted Answer

Increasing the sample size reduces the standard error, which narrows the confidence interval. Decreasing the confidence level also narrows the interval because it requires less certainty.

A 90% Confidence Interval for the Average Salary of All