16. An IRS auditor only has time to audit two of three tax returns. Suppose two of the tax returns show that the taxpayer owes the IRS. Assume that the IRS auditor is to randomly select two of the returns. Let R denote the event of refund and N denote the event of non-refund (owe). Define the random variable X to equal the number of tax returns among the two selected. What of the following statement is incorrect? (A) The outcome of this experiment is RR, NR, NN. (B) The possible outcome of X is 0, 1, 2. (C) P[RR] = 4 / 9 (D) P[NR] = 2 / 9 (E) P[NN] = 1 / 9

18. Airline overbooking is a common practice. Many people make reservations on several flights due to uncertain plans and then cancel at the last minute or simply fail to show up. Eagle Air is a small commuter airline. Its planes hold only 15 people. Past records indicate that 20% of the people making a reservation do not show up for the flight. Let X denote the number of people making a reservation but do not show up for the flight out of 15 passengers. Assume X is a binomial random variable. What of the following statement is incorrect? (A) On a given flight, the probability that all passengers have seats is $0.2^{15}$. (B) The mean number of people making a reservation but do not show up for the flight equals 3. (C) The mean number of people making a reservation and show up for the flight equals 12. (D) The standard deviation of X equals 1.549. (E) The variance of X equals 2.4.

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