Chapter 5: Problem 16
Find the mean and standard deviation for a binomial distribution with these values: a. \(n=1000, p=.3\) b. \(n=400, p=.01\) c. \(n=500, p=.5\) d. \(n=1600, p=.8\)
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Chapter 5: Problem 16
Find the mean and standard deviation for a binomial distribution with these values: a. \(n=1000, p=.3\) b. \(n=400, p=.01\) c. \(n=500, p=.5\) d. \(n=1600, p=.8\)
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Fast Food and Gas Stations Forty percent of all Americans who travel by car look for gas stations and food outlets that are close to or visible from the highway. Suppose a random sample of \(n=25\) Americans who travel by car are asked how they determine where to stop for food and gas. Let \(x\) be the number in the sample who respond that they look for gas stations and food outlets that are close to or visible from the highway. a. What are the mean and variance of \(x ?\) b. Calculate the interval \(\mu \pm 2 \sigma\). What values of the binomial random variable \(x\) fall into this interval? c. Find \(P(6 \leq x \leq 14)\). How does this compare with the fraction in the interval \(\mu \pm 2 \sigma\) for any distribution? For mound-shaped distributions?
Consider the medical payment problem in Exercise 5.27 in a more realistic setting. Of all patients admitted to a medical clinic, \(30 \%\) fail to pay their bills and the debts are eventually forgiven. If the clinic treats 2000 different patients over a period of 1 year, what is the mean (expected) number of debts that have to be forgiven? If \(x\) is the number of forgiven debts in the group of 2000 patients, find the variance and standard deviation of \(x\). What can you say about the probability that \(x\) will exceed \(700 ?\) (HINT: Use the values of \(\mu\) and \(\sigma,\) along with Tchebysheff's Theorem, to answer this question.)
A psychiatrist believes that \(80 \%\) of all people who visit doctors have problems of a psychosomatic nature. She decides to select 25 patients at random to test her theory. a. Assuming that the psychiatrist's theory is true, what is the expected value of \(x\), the number of the 25 patients who have psychosomatic problems? b. What is the variance of \(x\), assuming that the theory is true? c. Find \(P(x \leq 14)\). (Use tables and assume that the theory is true.) d. Based on the probability in part \(\mathrm{c}\), if only 14 of the 25 sampled had psychosomatic problems, what conclusions would you make about the psychiatrist's theory? Explain.
If \(x\) has a binomial distribution with \(p=.5\), will the shape of the probability distribution be symmetric, skewed to the left, or skewed to the right?
A procedure often used to control the quality of name-brand food products utilizes a panel of five "tasters." Each member of the panel tastes three samples, two of which are from batches of the product known to have the desired taste and the other from the latest batch. Each taster selects the sample that is different from the other two. Assume that the latest batch does have the desired taste, and that there is no communication between the tasters. a. If the latest batch tastes the same as the other two batches, what is the probability that the taster picks it as the one that is different? b. What is the probability that exactly one of the tasters picks the latest batch as different? c. What is the probability that at least one of the tasters picks the latest batch as different?
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