Question

The age (in years) of cars currently on the road in the U.S. is normally distributed. A researcher from the firm IHS Automotive selected a random sample of 30 cars and calculated the interval [10.39, 12.61] as the 90% confidence interval for the average age. The margin of error is _____.

Answer 1

Answer: Tthe margin of error is 1.11.

Explanation:

We know that the confidence interval is given by :-

[Sample mean - Margin of error , Sample mean +Margin of error]

A researcher from the firm IHS Automotive selected a random sample of 30 cars and calculated the interval [10.39, 12.61] as the 90% confidence interval for the average age.

i.e. Sample mean - Margin of error= 10.39 ...(i)

Sample mean + Margin of error = 12.61 ...(ii)

Eliminate (i) from (ii), we get

2(Margin of error)=2.22

⇒Margin of error=1.11

Hence, the margin of error is 1.11.