Chapter 8: Q.10 (page 523)
It's about ME Explain how each of the following would affect the margin of error of a confidence interval, if all other things remained the same.
(a) Increasing the confidence level
(b) Quadrupling the sample size
(a) It increases the margin of error.
(b) It would reduce the margin of error.
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61. Willows in Yellowstone Writers in some fields summarize data by giving and its standard error rather than and . Biologists studying willow trees in Yellowstone National Park reported their results in a table with columns labeled . The table entry for the heights of willow trees (in centimeters) in one region of the park was The researchers measured a total of trees.
(a) Find the sample standard deviation for these measurements. Show your work.
(b) Explain why the given interval is not a confidence interval for the mean height of willow trees in this region of the park.
A researcher plans to use a random sample of families to estimate the mean monthly family income for a large population. Aconfidence interval based on the sample would be ______ than a 90% confidence interval.
(a) narrower and would involve a larger risk of being incorrect
(b) wider and would involve a smaller risk of being incorrect
(c) narrower and would involve a smaller risk of being incorrect
(d) wider and would involve a larger risk of being incorrect
(e) wider, but it cannot be determined whether the risk of being incorrect would be larger or smaller
True or false: The interval from to has a chance of containing the actual population standard deviation . Justify your answer.
The companyโs customer satisfaction survey.
In the companyโs prior-year survey, 80% of customers surveyed said they were โsatisfiedโ or โvery satisfied.โ Using this value as a guess for pห, find the sample size needed for a margin of error of 3% at a 95% confidence level.
You want to compute a confidence interval for the mean of a population with unknown population standard deviation. The sample size is . The value of role="math" localid="1649226392559" you would use for this interval is
(a)(b).(c)
(d) (e)
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