hypothesis test

14. Some manufacturers claim that non-hyblfid sedan cars have a lower mean miles-per- gallon (mpg) than hybrid ones. Suppose that consumers test 21 hybrid sedans and get a mean of 31 mpg with a standard deviation of seven mpg. Thirty-one nonhybrid sedans get a mean of 22 mpg with a standard deviation of four mpg. Suppose that the poplation standard deviations are known to be six and three, respectively. Conduct a hypothesis tat to evaluate the manufacturers claim