Gas Mileage
A car company says that mean gas mileage for its luxury sedan is at least 21 miles for each gallon (mpg). You believe the claim is incorrect and find out that a random sample of five cars has a mean gas mileage of 19 mpg and the standard deviation of 4 mpg. Suppose the gas mileage of all of the company's luxury sedans is normally distributed. At α = 0.05, test company's claim.