Chapter 5, Problem 9E

Guzzlers? Environmental Protection Agency (EPA) fuel economy estimates for automobile models tested recently predicted a mean of 24.8 mpg and a standard deviation of 6.2 mpg for highway driving. Assume that a Normal model can be applied.

1. a) Draw the model for auto fuel economy. Clearly label it, showing what the 68–95–99.7 Rule predicts.
2. b) In what interval would you expect the central 68% of autos to be found?
3. c) About what percent of autos should get more than 31 mpg?
4. d) About what percent of cars should get between 31 and 37.2 mpg?
5. e) Describe the gas mileage of the worst 2.5% of all cars.