In Example 5.4 shown below you and two friends decided to go to Wendy’s. Now, suppose that instead you go to Burger King, which recently filled approximately 90.5% of orders correctly. What is the probability that

a. All three orders will be filled correctly?

b. None of the three will be filled correctly?

c. At least two of the three will be filled correctly?

d. What are the mean and standard deviation of the binomial distribution used in (a) through (c)? Interpret these values.

e. Compare the result of (a) through (d) with those of Wendy’s in Example 5.4 on page 217 and McDonald’s in Problem 5.17.

Example 5.4

Accuracy in taking orders at a drive-through window is important for fast-food chains. Periodically, QSR Magazine publishes “The Drive-Thru Performance Study: Order Accuracy” that measures the percentage of orders that are filled correctly. In a recent month, the percentage of orders filled correctly at Wendy’s was approximately 86.9%.

Suppose that you go to the drive-through window at Wendy’s and place an order. Two friends of yours independently place orders at the drive-through window at the same Wendy’s. What are the probabilities that all three, that none of the three, and that at least two of the three orders will be filled correctly? What are the mean and standard deviation of the binomial distribution for the number of orders filled correctly?