# N1s 2 χ 2 l 1011065 2 67328 079 a clinical trial was

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(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.
Does the result indicate whether the treatment iseffective?
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."
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?
If the confidence level is 95%,what is the value ofα?
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?
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.
b.Identify the value of the margin of error E
c.Construct the confidence interval.
d.Write a statement that correctly interprets the confidence interval. Choose the correct answer below.
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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