Suppose that cars arrive at Burger King's drive through at the rate of 20 cars every hour between 12:00 noon and 1:00 pm. A random sample of 40 one-hour time periods between 12:00 noon and 1:00 pm is selected and has 22.1 as the mean number of cars arriving.
a. Why is the sampling distribution of x-bar approximately normal?
b. What is the mean and standard deviation of the sampling distribution of x-bar assuming that mean =20 and standard deviation equals the square root of 20?
c. What is the probability that a simple random sample of 40 one-hour time periods results in a mean of at least 22.1 cars? Is this result unusual? What might we conclude?