Download Homework 3 (Chapter 10

Homework 3 (Chapter 10.3, 10.4)
27. Annual starting salaries for college graduates with business administration degrees
are believed to have a standard deviation of approximately $2000. Assume that a 95%
confidence interval estimate of the mean annual starting salary is desired. How large a
sample should be taken if the margin of error is
a. $500? b. $200? c. $100?
29. The travel-to-work time for residents of the 15 largest cities in the United States is
reported in the 1998 Information Please Almanac. Suppose that a preliminary simple
random sample of residents of San Francisco is used to develop a planning value of
6.25 minutes for the population standard deviation.
a. If we want to estimate the population mean travel-to-work time for San Francisco
residents with a margin of error of 2 minutes, what sample size should be used?
Assume a 95% confidence level.
b. If we want to estimate the population mean travel-to-work time for San Francisco
residents with a margin of error of 1 minutes, what sample size should be used?
Assume a 95% confidence level.
31. A simple random sample of 400 individuals provided 100 Yes responses.
a. What is the point estimate of the proportion of the population who would provide
Yes responses?
b. What is the standard error of the proportion,
P?
c. Compute the 95% confidence interval for the population proportion.
35. A Time/CNN poll asked 814 adults respond to a series of questions about their
feelings toward the state of affairs within the United States. A total of 562 adults
responded Yes to the question: Do you feel things are going well in the United States
these days? (Time, August 11, 1997).
a. What is the point estimate of the proportion of the adult population who feel things
are going well in the United States?
b. At a 90% confidence level, what is the margin of error?
c. What is the 90% confidence interval for the proportion of the adult population who
feel things are going well in the United States?
38. Audience profile data collected at the ESPN SportsZone web site showed that
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26% of the users were women (U.S.A. Today, January 21, 1998). Assume that this
percentage was based on a sample of 400 users.
a. At the 95% confidence level, what is the margin of error associated with the
estimated proportion of users who are women?
b. What is the 95% confidence interval for the population proportion of ESPN
Sports-Zone web site users who are women?
c. How large a sample should be taken if the desired margin of error is 3%?
39.The Tourism Institute for the State of Florida plans to sample visitors at major
beaches throughout the state to estimate the proportion of beach visitors who are not
Florida residents. Preliminary estimates are that 55% of the beach visitors are not
Florida residents.
a. How large a sample should be taken to estimate the proportion of out-of-state
visitors with a margin of error of 3%? Use a 95% confidence level.
b. How large a sample should be taken if the margin of errors is increased to 6%?
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