Chapter 7: Problem 69
How does the value of \(\sigma_{\hat{p}}\) change as the sample size increases? Explain. Assume \(n / N \leq .05\).
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Chapter 7: Problem 69
How does the value of \(\sigma_{\hat{p}}\) change as the sample size increases? Explain. Assume \(n / N \leq .05\).
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A population has a normal distribution. A sample of size \(n\) is selected from this population. Describe the shape of the sampling distribution of the sample mean for each of the following cases. a. \(n=23\) b. \(n=450\)
For a population, \(\mu=125\) and \(\sigma=36\). a. For a sample selected from this population, \(\mu_{\bar{x}}=125\) and \(\sigma_{\bar{x}}=3.6 .\) Find the sample size. Assume \(n / N \leq .05\). b. For a sample selected from this population, \(\mu_{\bar{x}}=125\) and \(\sigma_{\bar{x}}=2.25 .\) Find the sample size. Assume \(n / N \leq .05\).
Refer to Exercise 7.79. Beginning in the second half of 2011 , there were widespread protests in many American cities that were primarily against Wall Street corruption and the gap between the rich and the poor in America. According to a Time Magazine/ABT SRBI poll conducted by telephone during October \(9-10,2011,86 \%\) of adults who were familiar with those protests agreed that Wall Street and lobbyists have too much influence in Washington (The New York Times, October 22, 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 400 American adults who hold the opinion that Wall Street and lobbyists have too much influence in Washington. Find the probability that the value of \(\hat{p}\) will be a. greater than \(.88\) b. between \(.82\) and 84
The GPAs of all 5540 students enrolled at a university have an approximately normal distribution with a mean of \(3.02\) and a standard deviation of \(.29 .\) Let \(\bar{x}\) be the mean GPA of a random sample of 48 students selected from this university. Find the mean and standard deviation of \(\bar{x}\), and comment on the shape of its sampling distribution.
A city is planning to build a hydroelectric power plant. A local newspaper found that \(53 \%\) of the voters in this city favor the construction of this plant. Assume that this result holds true for the population of all voters in this city. a. What is the probability that more than \(50 \%\) of the voters in a random sample of 200 voters selected from this city will favor the construction of this plant? b. A politician would like to take a random sample of voters in which more than \(50 \%\) would favor the plant construction. How large a sample should be selected so that the politician is \(95 \%\) sure of this outcome?
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