A car-rental company is interested in the amount of time its vehicles are out of operation for repair work. State all assumptions and find a 90%

confidence interval for the mean number of days in a year that all vehicles in the company's fleet are out of operation if a random sample of 10 cars showed the following number of days that each had been inoperative.

20

16

11

23

19

13

8

12

15

29

State all assumptions. Select all the assumptions below.

A.

The variance is less than the mean

B.

It is a random sample

C.

The sample comes from a normal population

D.

The sample size is at least 30

Find a 90%

confidence interval for the population mean.

The 90%

confidence interval is from a lower limit of _____ to an upper limit of _____ .