num 15

A fleet of rental cars - all the same make, model, and year - has a mean fuel efficiency of 25 miles per gallon (mpg). A random sample of 57 cars are selected and the air filter of each is replaced with a new one. Let be the population mean fuel efficiency score that would occur if every car's air filter were replaced. The air filter change is deemed effective if u>25mpg. A test is made of H0:u=25 versus H1:u>25 . Consider these possible conclusions: i). The air filter changes are effective. ii). The air filter changes are not effective. iii). The air filter changes might not be effective.

Which of the three conclusions is best if H0 is not rejected? Question 15 options:

i

iii

ii