Chapter 7: Problem 12
How does the value of \(\sigma_{\bar{x}}\) change as the sample size increases? Explain.
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Chapter 7: Problem 12
How does the value of \(\sigma_{\bar{x}}\) change as the sample size increases? Explain.
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According to Moebs Services Inc., an individual checking account at U.S. community banks costs these banks between $$\$ 175$$ and $$\$ 200$$ per year (Time, November 21,2011 ). Suppose that the average annual cost of all such checking accounts at U.S. community banks is $$\$ 190$$ with a standard deviation of $$\$ 20.$$ Find the probability that the average annual cost of a random sample of 100 such checking accounts at U.S. community banks is a. less than $$\$ 187$$ b. more than $$\$ 193.5$$ c. $$\$ 191.70$$ to $$194.5$$
The GPAs of all students enrolled at a large university have an approximately normal distribution with a mean of \(3.02\) and a standard deviation of \(.29 .\) Find the probability that the mean GPA of a random sample of 20 students selected from this university is a. \(3.10\) or higher b. \(2.90\) or lower c. \(2.95\) to \(3.11\)
According to the Project on Student Debt, the average student loan for college graduates of the class of 2010 was $$\$ 25.000$$ (USA TODAY, April 24, 2012). Suppose that the student loans for all college graduates of the class of 2010 have a mean of $$\$ 25,000$$ and a standard deviation of $$\$ 6280 .$$ Let \(\bar{x}\) be the average student loan of a random sample of 400 college graduates from the class of \(2010 .\) Find the mean and standard deviation of the sampling distribution of \(\bar{x}\)
If all possible samples of the same (large) size are selected from a population, what percentage of all the sample means will be within \(2.5\) standard deviations \(\left(\sigma_{\bar{x}}\right)\) of the population mean?
Let \(\hat{p}\) be the proportion of elements in a sample that possess a characteristic. a. What is the mean of \(\hat{p}\) ? b. What is the formula to calculate the standard deviation of \(\hat{p} ?\) Assume \(n / N \leq .05\). c. What condition(s) must hold true for the sampling distribution of \(\hat{p}\) to be approximately normal?
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