Question 7 (15 marks) SECTION 3 A car manufacturer states that its new model does 32.5 miles per gallon (mpg). A recent independent study of 50 of the new cars showed a mean mpg of only 30.4 with a...

Question 7 (15 marks)

SECTION 3

A car manufacturer states that its new model does 32.5 miles per gallon (mpg). A recent independent study of 50 of the new cars showed a mean mpg of only 30.4 with a standard deviation of 5.3 mpg. Test the view that the manufacturer’s claim is too high using a 1% level of significance (1% critical value for Z = -2.33).

Question 8 (15 marks)

The expected life of a car engine in an electric car is claimed to be 90,000 miles. A sample of 190 electric cars gives a mean life of 96,700 miles with a standard deviation of 37,500 miles. Test whether the electric cars are lasting longer than expected at the 1% level of significance (1% critical value for Z = -2.33).