HW_7_S11

HW_7_S11 - AEM 2100 Spring 2011 Homework 7 1 Name A study...

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AEM 2100 Name: _________________ Spring 2011 Homework 7 1.) A study of drivers reveals that, when lost, 45% will stop and ask for directions, 30% will consult a map, and 25% will continue driving until the location has been determined. Suppose that a sample of 200 drivers was asked to report what they do when lost. Find the following probabilities. a.) at least 100 stop and ask directions. b.) at most 55 continue driving. c.) between 50 and 75 (inclusive) consult a map. 2.) Time spent using e-mail per session is normally distributed with a mean of 8 minutes and a standard deviation of 2 minutes. If you select a random sample of 25 sessions: a.) what is the probability that the sample mean is between 7.8 and 8.2 minutes? b.) what is the probability that the sample mean is between 7.5 and 8 minutes? c.) If you select a random sample of 100 sessions, what is the probability that the sample mean is between 7.8 and 8.2 minutes? d.) Explain the difference in the results of (a) and (c). 3.) The amount of time spent by North American adults watching television per day is normally distributed with a mean of 6 hours and a standard deviation of 1.5 hours. a.) What is the probability that a randomly selected North American adult watches television for more than 7 hours? b.) What is the probability that the average time watching television by a random sample of five North American adults is more than 7 hours? c.) What is the probability that, in a random sample of five North American adults, all watch television for more than 7 hours per day?

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4.) The probability of flu symptoms for a person not receiving any treatment is 0.019. In a clinical trial of Lipitor, a drug commonly used to lower cholesterol, 863 patients were given a treatment of 10-mg Lipitor tablets, and 19 of those patients experienced flu symptoms (Based on data from Pfizer, Inc.) Assuming that these tablets have no effect on flu symptoms, estimate the probability that at least 19 of
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HW_7_S11 - AEM 2100 Spring 2011 Homework 7 1 Name A study...

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