Answered: A New York Times/CBS poll asked the…

MATLAB: An Introduction with Applications

6th Edition

ISBN:9781119256830

Author:Amos Gilat

Publisher:Amos Gilat

Chapter1: Starting With Matlab

Section: Chapter Questions

Problem 1P

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1.A New York Times/CBS poll asked the question, "What do you think is the most important problem facing this country today?" It found that twenty-four percent of the respondents answered "crime and violence." The margin of sampling error was plus or minus 2.7 percentage points. Following the convention that the margin of error was based on a 95% confidence interval, find the 95% confidence interval for the percentage of the population that would respond "crime and violence" to the question asked by the pollsters. (Express answers as decimal numbers to 3 places.)

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2.A random sample of medical files is used to estimate the proportion p of all people who have blood type B.

(a) If you have no preliminary estimate for p, how many medical files should you include in a random sample in order to be 98% sure that the point estimate p̂ will be within a distance of 0.030 from p?

(b) Answer part (a) if you use the preliminary estimate that about 7 out of 90 people have blood type B.

3.How hard is it to reach a businessperson by phone? Let p be the proportion of calls to businesspeople for which the caller reaches the person being called on the first try.

(a) If you have no preliminary estimate for p, how many business phone calls should you include in a random sample to be 95% sure that the point estimate p̂ will be within a distance of 0.060 from p?

(b) A report states that business-people can be reached by a single phone call approximately 22% of the time. Using this national estimate for p, answer part (a).

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