答案和详解如下： Q1. There is a 40% chance that the economy will be good next year and a 60% chance that it will be bad. If the economy is good, there is a 50 percent chance of a bull market, a 30% chance of a normal market, and a 20% chance of a bear market. If the economy is bad, there is a 20% chance of a bull market, a 30% chance of a normal market, and a 50% chance of a bear market. What is the joint probability of a good economy and a bull market? A) 50%. B) 20%. C) 12%. Correct answer is B) Joint probability is the probability that both events, in this case the economy being good and the occurrence of a bull market, happen at the same time. Joint probability is computed by multiplying the individual event probabilities together: (0.40) × (0.50) = 0.20 or 20%.
Q2. What is the probability of a bull market next year? A) 32%. B) 20%. C) 50%. Correct answer is A) Because a good economy and a bad economy are mutually exclusive, the probability of a bull market is the sum of the joint probabilities of (good economy and bull market) and (bad economy and bull market): ((0.40) × (0.50)) + ((0.60) × (0.20)) = 0.32 or 32%. Q3. For a stock, which of the following is least likely a random variable? Its: A) stock symbol. B) current ratio. C) most recent closing price. Correct answer is A) A random variable must be a number. Sometimes there is an obvious method for assigning a number, such as when the random variable is a number itself, like a P/E ratio. A stock symbol of a randomly selected stock could have a number assigned to it like the number of letters in the symbol. The symbol itself cannot be a random variable. Q4. If two events are mutually exclusive, the probability that they both will occur at the same time is: A) 0.00. B) 0.50. C) Cannot be determined from the information given. Correct answer is A) If two events are mutually exclusive, it is not possible to occur at the same time. Therefore, the P(A∩B) = 0. Q5. Which of the following statements about probability is most accurate? A) An outcome is the calculated probability of an event. B) A conditional probability is the probability that two or more events will happen concurrently. C) An event is a set of one or more possible values of a random variable. Correct answer is C) Conditional probability is the probability of one event happening given that another event has happened. An outcome is the numerical result associated with a random variable. | 
发表于 2009-1-9 08:52
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