9709 P62 - Mar 2021 - Q6 - 10 marks
10338
It is known that 8% of adults in a certain town own a Chantor car. After an advertising campaign, a car dealer wishes to investigate whether this proportion has increased. He chooses a random sample of 25 adults from the town and notes how many of them own a Chantor car.
(a) He finds that 4 of the 25 adults own a Chantor car.
(a) Carry out a hypothesis test at the 5% significance level. [5]
(b) Explain which of the errors, Type I or Type II, might have been made in carrying out the test in part (a). [2]
Later, the car dealer takes another random sample of 25 adults from the town and carries out a similar hypothesis test at the 5% significance level.
(c) Find the probability of a Type I error. [3]
