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Chapter 8: Q.44 (page 479)
Define the random variable X in words.
The random variable indicates the amount of time Americans spend watching television every month.
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The average height of young adult males has a normal distribution with a standard deviation of 2.5 inches. You want to estimate the mean height of students at your college or university to within one inch with 93 per cent confidence. How many male students must you measure?
Suppose randomly selected people are surveyed to determine if they own a tablet. Of the surveyed, reported owning a tablet. Using a% confidence level, compute a confidence interval estimate for the true proportion of people who own tablets
132. Public Policy Polling recently conducted a survey asking adults across the U.S. about music preferences. When asked, of the participants admitted that they have illegally downloaded music.
a. Create a confidence interval for the true proportion of American adults who have illegally downloaded music.
b. This survey was conducted through automated telephone interviews on May 6 and 7,2013. The error bound of the survey compensates for sampling error or natural variability among samples. List some factors that could affect the survey's outcome that is not covered by the margin of error.
c. Without performing any calculations, describe how the confidence interval would change if the confidence level changed from .
Suppose we have data from a sample. The sample mean is , and the error bound for the mean is . What is the confidence interval estimate for the population mean?
124. Refer to Exercise 8.123. Another question in the poll was "[How much are) you worried about the quality of education in our schools?" Sixty-three percent responded "a lot". We are interested in the population proportion of adult Americans who are worried a lot about the quality of education in our schools.
b. Which distribution should you use for this problem? Explain your choice.
c. Construct a confidence interval for the population proportion of adult Americans who are worried a lot about the quality of education in our schools.
i. State the confidence interval.
ii. Sketch the graph.
iii. Calculate the error bound.
d. The sampling error given by Yanklovich Partners, Inc. (which conducted the poll) is . In one to three complete sentences, explain what the represents.
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