(n−1)s2χ2L=(101−1)(0.65)267.328=0.79

A clinical trial was conducted to test the effectiveness of a drug used for treating insomnia in older subjects. Aftertreatment with the drug, 23 subjects had a mean wake time of 93.3 min and a standard deviation of 40.2 min. Assume thatthe 23 sample values appear to be from a normally distributed population and construct a 98% confidence intervalestimate of the standard deviation of the wake times for a population with the drug treatments. Does the result indicatewhether the treatment is effective? Find the confidence interval estimate.

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Does the result indicate whether the treatment iseffective?

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QUIZA magazine provided results from a poll of 1500adults who were asked to identify their favorite pie. Among the 1500respondents, 14%chose chocolatepie, and the margin of error was given as ±4percentage points. Describe what ismeant by the statement that"the margin of error was given as ±4percentagepoints."

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A magazine provided results from a poll of 2000adults who were asked to identify their favorite pie. Among the 2000respondents, 14%chose chocolatepie, and the margin of error was given as ±4percentage points. What values dop, q,n, E, and prepresent? If the confidence level is 95%,what is the value ofα?

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If the confidence level is 95%,what is the value ofα?

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A newspaper provided a"snapshot" illustrating poll results from 1910 professionals who interview job applicants. Theillustration showed that26% of them said the biggest interview turnoff is that the applicant did not make an effort to learnabout the job or the company. The margin of error was given as ±3percentage points. What important feature of the pollwasomitted?

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Use the sample data and confidence level given below to complete parts (a) through (d).A research institute poll asked respondents if they felt vulnerable to identity theft. In the poll, n=905 and x=576who said "yes." Use a 95% confidence level.a.Find the best point estimate of the population proportion p.

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b.Identify the value of the margin of error E

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c.Construct the confidence interval.

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d.Write a statement that correctly interprets the confidence interval. Choose the correct answer below.

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Assume that the sample is a simple random sample obtained from a normally distributed population of IQ scores ofstatistics professors. Use the table below to find the minimum sample size needed to be 99%confident that the samplestandard deviation s is within 20%ofσ.Is this sample sizepractical?

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