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Chapter 8: Q 8.4RP. (page 346)
If you obtained one thousand confidence intervals for a population mean. , roughly how many of the intervals would actually contain ?
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Northeast Commutes. Refer to Exercise
a. Determine and interpret a upper confidence bound for the mean commute time of all commuters in Washington, DC.
b. Compare your one-sided confidence interval in part (a) to the (twosided) confidence interval found in Exercise
When estimating an unknown parameter, what does the margin of error indicate?
State True or False. Give Reasons for your answers..
The confidence interval can be obtained if you know only the margin of error.
Christmas Spending. In a national poll of U.S. adults, conducted November, Gallup asked "Roughly how much money do you think you personally will spend on Christmas gifts this year?". The data provided on the Weiss Stats site are based on the results of the poll.
a. Determine a upper confidence bound for the mean amount spent on Christmas gifts in (Note: The sample mean and sample standard deviation of the data are and , respectively.)
b. Interpret your result in part (a).
c. In , the mean amount spent on Christmas gifts was . Comment on this information in view of your answer to part (b).
A confidence interval for a population mean has a margin of error of
a. Determine the length of the confidence interval.
b. If the sample mean is , obtain the confidence interval.
c. Construct a graph that illustrates your results.
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