Question

It is known that the amount of time needed to change the oil on a car is normally distributed with a standard deviation of 5 minutes. The amount of time to complete a random sample of 10 oil changes was recorded and listed here. Compute the 99% confidence interval estimate of the mean of the population.

Answer 1

-4.08 <x< 4.08

Explanation:

For the given information,

`\sigma = 5\\n= 10\\ci = 99%`

From the tables for 99% confidence interval we have a Z-value of 2.58

`Range= z*(\sigma)/(√(n))\\Range= (2.58)(5)/(√(10))\\Range = 4.08`

`-4.08 <x< 4.08`