Chapter 7: Problem 27
Explain the central limit theorem.
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Chapter 7: Problem 27
Explain the central limit theorem.
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The times that college students spend studying per week have a distribution that is skewed to the right with a mean of \(8.4\) hours and a standard deviation of \(2.7\) hours. Find the probability that the mean time spent studying per week for a random sample of 45 students would be a. between 8 and 9 hours b. less than 8 hours
In a Time/Money Magazine poll of Americans age 18 years and older, \(65 \%\) agreed with the statement, "We are less sure our children will achieve the American Dream" (Time, October 10,2011 ). Assume that this result is true for the current population of Americans age 18 years and older. Let \(\hat{p}\) be the proportion in a random sample of 600 Americans age 18 years and older who agree with the above statement. Find the mean and standard deviation of the sampling distribution of \(\hat{p}\) and describe its shape.
For a population, \(N=30,000\) and \(p=.59 .\) Find the \(z\) value for each of the following for \(n=100\). a. \(\hat{p}=.56\) \(\begin{array}{lll}\text { b. } \hat{p}=.68 & \text { c. } \hat{p}=.53 & \text { d. } \hat{p}=.65\end{array}\)
In a Time Magazine/Aspen poll of American adults conducted by the strategic research firm Penn Schoen Berland, these adults were asked, "In your opinion, what is more important for the U.S. to focus on in the next decade?" Eighty- three percent of the adults polled said domestic issues (Time, July 11,2011 ). Assume that this percentage is true for the current population of American adults. Let \(\hat{p}\) be the proportion in a random sample of 1000 American adults who hold the above opinion. Find the mean and standard deviation of the sampling distribution of \(\hat{p}\) and describe its shape.
Suppose that the incomes of all people in the United States who own hybrid (gas and electric) automobiles are normally distributed with a mean of \(\$ 78,000\) and a standard deviation of \(\$ 8300\). Let \(\bar{x}\) be the mean income of a random sample of 50 owners of such automobiles. Calculate the mean and standard deviation of \(\bar{x}\) and describe the shape of its sampling distribution.
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