Exam 17: Additional Topics in Sampling

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: In a stratified random sample of students on a campus,sample members were asked to rate,on a scale of 1 (poor)to 5 (excellent),opportunities for improving the college infrastructure.The results are shown in the table below. -If a total sample of 150 students is taken,determine the number of juniors and seniors under the optimum allocation scheme,assuming that the stratum population standard deviations are the same as the corresponding sample values.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A chemistry class at a university in the Midwest has 450 students.The final examination is optional - it can raise,but not lower,a student's grade.Of a random sample of 100 students,40 indicated that they would take the final examination. -Find a 90% confidence interval for the proportion of students intending to take the final examination.

Compared with optimal allocation,proportional allocation allocates relatively more sample effort to strata in which the population variance is highest.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A corporation has 30 outlets in the North,40 in the South,60 in the Midwest,and 45 in the West.Using a proportional allocation of a random sample of 20% of the outlets,the manager records the following means and standard deviations. -Describe two methods of nonprobabilistic sampling methods.Give an example for each.What are the advantages and disadvantages of each?

For a sample of 75 observations from a population of 573,the sample mean is 33.2 and the sample standard deviation is 3.6.Develop a 95% confidence interval for the population mean.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A sales representative has 425 accounts.From a random sample of 60 of these accounts,she found that the average yearly order was $1,250 with a standard deviation of $70.She also found that 28 out of 60 in the sample have placed an order in the last four weeks. -Which of the following is an example of a nonprobabilistic sampling technique?

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The faculty advisor for the finance society at a local business school is interested in determining the proportion of finance students going on a field trip.The advisor samples some students from each class and computes the sample proportion for each class. -Estimate the proportion of all students going on the field trip.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A sales representative has 425 accounts.From a random sample of 60 of these accounts,she found that the average yearly order was $1,250 with a standard deviation of $70.She also found that 28 out of 60 in the sample have placed an order in the last four weeks. -Find the 90% confidence interval for the proportion of all accounts that placed an order within the last four weeks.

The use of proportional allocation in stratified sampling implies that the same number of elements is sampled in each stratum.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: In a stratified random sample of students on a small campus,sample members were asked to rate,on a scale of 1 (poor)to 5 (excellent),opportunities for extracurricular activities.The results are shown in the table below. -Find a 95% confidence interval for the mean rating given by all freshmen and sophomores on the campus.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: In a stratified random sample of students on a campus,sample members were asked to rate,on a scale of 1 (poor)to 5 (excellent),opportunities for improving the college infrastructure.The results are shown in the table below. -If a total sample of 150 students is taken,determine the number of freshmen and sophomores under the optimum allocation scheme,assuming that the stratum population standard deviations are the same as the corresponding sample values.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: An auditor is faced with reviewing 1,294 invoices.From a random sample of 122 of these accounts,she found that the average amount was $639 with a standard deviation of $143.She also found that 37 out of the 122 in the sample were from out-of-state suppliers. -Find a 95% confidence interval for the proportion of all invoices that are from out-of-state suppliers.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: The U.S.Senate has 100 members.62 senators' offices obtained certain information from the individuals responsible for managing correspondence.Of these,40 specified a minimum number of letters that must be received on an issue before a form letter in response is created. -What is quota sampling? States its advantages and disadvantages.

In stratified random sampling,the stratum sample mean is a biased estimator of the population mean.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: In a stratified random sample of students on a campus,sample members were asked to rate,on a scale of 1 (poor)to 5 (excellent),opportunities for improving the college infrastructure.The results are shown in the table below. -If a total sample of 150 students is taken,determine the number of juniors and seniors under the proportional allocation scheme.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: An auditor,examining a total of 650 accounts receivable by a corporation,selected a random sample of 45 accounts.The sample mean is $108.34 and the sample standard deviation is $30.85. -A director of marketing research needs a sample of households to participate in the testing of a new toothpaste package.She directs five members of her staff to find five households each.This is an example of:

The sample size for the j^th stratum using proportional allocation is n_j = × n.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: A supermarket chain has 25 stores in the North,30 in the South,50 in the Midwest,and 35 in the West.Using a proportional allocation of a random sample of 30% of the outlets,the manager records the following means and standard deviations. -Find a 95% confidence interval for the population mean.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: Of the 1400 colleges in the United States,370 have two-year schools and 1030 have four-year schools.In a random sample of 40 two-year schools,it was found that 10 of the schools do not have any faculty holding a Ph.D.degree.In an independent random sample of 60 four-year schools,it was found that only 6 of the schools do not have any faculty holding a Ph.D.degree. -Find a 95% confidence interval for the proportion of all colleges that do not have any faculty holding a Ph.D.degree.

THE NEXT QUESTIONS ARE BASED ON THE FOLLOWING INFORMATION: In a stratified random sample of students on a campus,sample members were asked to rate,on a scale of 1 (poor)to 5 (excellent),opportunities for improving the college infrastructure.The results are shown in the table below. -Find a 90% confidence interval for the mean rating given by all juniors and seniors on the campus.