答案和详解如下： 1、A random variable that has a countable number of possible values is called a: A) discrete random variable. B) continuous random variable. C) probability distribution. D) binomial random variable. The correct answer was A) A discrete random variable is one for which the number of possible outcomes are countable, and for each possible outcome, there is a measurable and positive probability. A continuous random variable is one for which the number of outcomes is not countable. 2、Which of the following is least likely to be an example of a discrete random variable? A) Quoted stock prices on the NASDAQ. B) The rate of return on a real estate investment. C) The number of days of sunshine in the month of May 2006 in a particular city. D) The number of shareholders of General Electric common stock. The correct answer was B) The rate of return on a real estate investment, or any other investment, is an example of a continuous random variable because the possible outcomes of rates of return are infinite (e.g., 10.0%, 10.01%, 10.001%, etc.). All the other choices are measurable (countable). 3、Assume a discrete distribution for the number of possible sunny days in Provo, Utah during the week of April 20 through April 26. For this discrete distribution, p(x) = 0 when x cannot occur, or p(x) > 0 if it can. Based on this information, what is the probability of it being sunny on 5 days and on 10 days during the week? 5 Days of Sunshine 10 Days of Sunshine
A) A positive value Infinite B) Zero Infinite C) A positive value Zero D) A negative value Zero The correct answer was C) The probability of it being sunny on 5 days during the week has some positive value, but the probability of having sunshine 10 days within a week of 7 days is zero because this cannot occur. | 
发表于 2008-4-10 14:04
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