4 Chapter Quiz 228 CHAPTER 4 Discrete Probability Distributions Take this quiz as you would take a quiz in class. After you are done, check your work against the answers given in the back of the book. 1. Determine whether the random variable x is discrete or continuous. Explain your reasoning. (a) Let x represent the number of lightning strikes that occur in Wyoming during the month of June. (b) Let x represent the amount of fuel (in gallons) used by a jet during takeoff. (c) Let x represent the final score in a game of bowling. 2. The table lists the number of wireless devices per household in a small town in the United States. Wireless devices 0 1 2 3 4 5 Number of households 277 471 243 105 46 22 (a) Construct a probability distribution. (b) Graph the probability distribution using a histogram and describe its shape. (c) Find the mean, variance, and standard deviation of the probability distribution and interpret the results. (d) Find the probability of randomly selecting a household that has at least four wireless devices. 3. In the past year, thirty-three percent of U.S. adults have put off medical treatment because of the cost. You randomly select nine U.S. adults. Find the probability that the number who have put off medical treatment because of the cost in the past year is (a) exactly three, (b) at most four, and (c) more than five. (Source: Gallup) 4. The five-year survival rate of people who undergo a liver transplant is 75%. The surgery is performed on six patients. (Source: Mayo Clinic) (a) Construct a binomial distribution. (b) Graph the binomial distribution using a histogram and describe its shape. (c) Find the mean, variance, and standard deviation of the binomial distribution and interpret the results. 5. An online magazine finds that the mean number of typographical errors per page is five. Find the probability that the number of typographical errors found on any given page is (a) exactly five, (b) less than five, and (c) exactly zero. 6. Basketball player Stephen Curry makes a 3-pointer about 43% of the time. Find the probability that (a) the first 3-pointer he makes is the third shot, (b) the first 3-pointer he makes is the fourth or fifth shot, and (c) he does not make his first six shots. (Source: ESPN) 7. Which event(s) in Exercises 5 and 6 can be considered unusual? Explain your reasoning.
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