Chapter 8: Q 8.31 (page 330)
For what is normal population an abbreviation?
It mean variables are normally distributed.
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Civilian Labor Force. Consider again the problem of estimating the mean age, , of all people in the civilian labor force. In Example on page 328 , we found that a sample size of 2250 is required to have a margin of error of year and a confidence level. Suppose that, due to financial constraints, the largest sample size possible is 900 . Determine the greatest confidence level, given that the margin of error is to be kept at half year. Recall that years.
Medical Marijuana. An issue with legalization of medical marijuana is "diversion," the process in which medical marijuana prescribed for one person is given, traded, or sold to someone who is not registered for medical marijuana use. Researchers S. Sautel et al. study the issue of diversion in the article "Medical Marijuana Use Among Adolescents in Substance Abuse Treatment" . The mean number of days that adolescents in substance abuse treatment used medical marijuana in the last six months was . Assume the population standard deviation is days.
a. Find a confidence interval for the mean number of days, , of diverted medical marijuana use in the last 6 months of all adolescents in substance abuse treatment.
b. Repeat part (a) at a confidence level.
c. Draw a graph similar to Fig. on page to display both confidence intervals.
d. Which confidence interval yields a more accurate estimate of ? Explain your answer.
Northeast Commutes. Refer to Exercise
a. Determine and interpret a upper confidence bound for the mean commute time of all commuters in Washington, DC.
b. Compare your one-sided confidence interval in part (a) to the (twosided) confidence interval found in Exercise
Assume that the population standard deviation is known and decide weather use of the z-interval procedure to obtain a confidence interval for the population mean is reasonable. Explain your answers.
The sample data contain no outliers, the variable under consideration is roughly normally distributed, and the sample size is .
Explain the effect on the margin of error and hence the effect on the accuracy of estimating a population mean by a sample mean.
Decreasing the confidence level while keeping the same sample size.
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