Chapter 8: Problem 7
Briefly explain the difference between a confidence level and a confidence interval.
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Chapter 8: Problem 7
Briefly explain the difference between a confidence level and a confidence interval.
These are the key concepts you need to understand to accurately answer the question.
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A random sample of 25 life insurance policyholders showed that the average premium they pay on their life insurance policies is \(\$ 685\) per year with a standard deviation of \(\$ 74\). Assuming that the life insurance policy premiums for all life insurance policyholders have a normal distribution, make a \(99 \%\) confidence interval for the population mean, \(\mu\).
A marketing researcher wants to find a \(95 \%\) confidence interval for the mean amount that visitors to a theme park spend per person per day. She knows that the standard deviation of the amounts spent per person per day by all visitors to this park is \(\$ 11\). How large a sample should the researcher select so that the estimate will be within \(\$ 2\) of the population mean?
According to a Pew Research Center nationwide telephone survey of adults conducted March 15 to April 24, 2011, \(69 \%\) of college graduates said that their college education gave them maturity (Time, May 30,2011 ). Suppose that this survey included 1450 college graduates. a. What is the point estimate of the corresponding population proportion? b. Construct a \(95 \%\) confidence interval for the proportion of all college graduates who will say that their college education gave them maturity. What is the margin of error for this estimate?
When calculating a confidence interval for the population mean \(\mu\) with a known population standard deviation \(\sigma\), describe the effects of the following two changes on the confidence interval: (1) doubling the sample size, (2) quadrupling (multiplying by 4) the sample size. Give two reasons why this relationship does not hold true if you are calculating a confidence interval for the population mean \(\mu\) with an unknown population standard deviation.
In a random sample of 50 homeowners selected from a large suburban area, 19 said that they had serious problems with excessive noise from their neighbors. a. Make a \(99 \%\) confidence interval for the percentage of all homeowners in this suburban area who have such problems. b. Suppose the confidence interval obtained in part a is too wide. How can the width of this interval be reduced? Discuss all possible alternatives. Which option is best?
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