Question: A car rental company is interested in the amount of time its vehicles are out of operation for repair work. A random sample of nine cars showed that over the past year, the number of days each had been inoperative were

16 10 21 22 8 17 19 14 19

Stating any assumptions you need to make, 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.