Since 1975 the average fuel efficiency of U.S. cars and

Last updated: 7/26/2022

Since 1975 the average fuel efficiency of U.S. cars and light trucks (SUVs) has increased from 13.5 to 25.8 mpg, an increase of over 90%. A random sample of 73 cars from a large community got a mean mileage of 29.96 mpg per vehicle. The population standard deviation is 4 mpg. Estimate the upper bound true mean gas mileage with 95% confidence.