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Chapter 8: Q.5 (page 524)
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)
(b)
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Starting a nightclub A college student organization wants to start a nightclub for students under the age of . To assess support for this proposal, they will select an SRS of students and ask each respondent if he or she would patronize this type of establishment. They expect that about % of the student body would respond favorably. What sample size is required to obtain a % con铿乨ence interval with an approximate margin of error of ? Show your work
Got shoes? The class in Exercise 1 wants to estimate the variability in the number of pairs of shoes that female students have by estimating the population variance .
Teens and their TV setsAccording to a Gallup Poll report, % of teens aged to have TVs in their rooms. Here is part of the footnote to this report:
These results are based on telephone interviews with a randomly selected national sample of teenagers in the Gallup Poll Panel of households, aged to . For results based on this sample, one can say . . . that the maximum error attributable to sampling and other random effects is percentage points. In addition to sampling error, question-wording and practical dif铿乧ulties in conducting surveys can introduce error or bias into the 铿乶dings of public opinion polls.
(a) We omitted the con铿乨ence level from the footnote. Use what you have learned to determine the con铿乨ence level, assuming that Gallup took an SRS.
(b) Give an example of a 鈥減ractical dif铿乧ulty鈥� that could lead to biased results for this survey.
Many television viewers express doubts about the validity of certain commercials. In an attempt to answer their critics, Timex Group USA wishes to estimate the proportion of consumers who believe what is shown in Timex television commercials. Let represent the true proportion of consumers who believe what is shown in Timex television commercials. What is the smallest number of consumers that Timex can survey to guarantee a margin of error of or less at a confidence level?
(a)
(b)
(c)
(d)
(c)
How common is SAT coaching? A random sample of students who took the SAT college entrance examination twice found that of the respondents had paid for coaching courses and that the remaining had not. Construct and interpret a confidence interval for the proportion of coaching among students who retake the SAT. Follow the four-step process.
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