Question

A car manufacturing company is interested in finding the average fuel consumption of one of its new models Leopard F-type. Hundred test drivers are chosen and asked to drive the car in urban conditions for 8 hours. The average fuel consumption of the 100 cars is found to be 30 miles per gallon (mpg) with a standard deviation of 6.2 mpg. Find the 99% confidence interval for the average fuel consumption of Leopard F-type. If the management says that the length of the confidence interval should not be greater than 1 mpg’s, what is the minimum number of test drivers required? If it is not possible to hire new drivers, how confident would you be about a CI with length 1 mpg?