Have to work on excel attached. All the formula needs to be seen.
Chapter 7 Q#9 Page 319, use data P02_16.xlsx
9. The file P02_16.xlsx contains traffic data from 256 weekdays on four variables. Each variable lists the num-ber of arrivals during a specific 5-minute period of the day. For this problem, consider this data set a simple random sample from all possible weekdays. a. For each of the four variables, find the sample mean. If each of these is used as an estimate from the cor-responding (unknown) population mean, is there any reason to believe that they either underestimate or overestimate the population means? Why or why not?
b. What are the (approximate) standard errors of the esti-mates in part a? How can you interpret these standard errors? Be as specific as possible.
c. Is it likely that the estimates in part a are accurate to within 0.4 arrival? Why or why not? (Answer for each variable separately.)
Chapter 7 Q#10 Page 319, use data P02_35.xlsx
10. The file P02_35.xlsx contains data from a survey of 500 randomly selected households. For this problem, con-sider this data set a simple random sample from all pos-sible households, where the number of households in the population is well over 1,000,000. a. Create a new variable, Total Income, that is the sum of First Income and Second Income.
b. For each of the four variables Total Income, Monthly Payment, Utilities, and Debt, find the sample mean. If each of these is used as an estimate from the cor-responding (unknown) population mean, is there any reason to believe that they either underestimate or overestimate the corresponding population means? Why or why not?
c. What are the (approximate) standard errors of the esti-mates in part b? How can you interpret these standard errors? Be as specific as possible. Is the finite popula-tion correction required? Why or why not?
d. Is it likely that the estimate of Total Income in part b is accurate to within $1500? Why or why not?
Chapter 8 Q#18 Page 342, use data P08_18.xlsx
18. Senior management of a large consulting firm is con-cerned about a growing decline in the organization’s weekly number of billable hours. Ideally, the organi-zation expects each professional employee to spend at
least 40 hours per week on work. The file P08_18.xlsx contains the work hours reported by a random sample of employees in a typical week. a. Calculate a 95% confidence interval for the mean number of hours worked by the company’s employees in a typical week.
b. Calculate a 95% confidence interval for the standard deviation of the number of hours worked by the com-pany’s employees in a typical week.
c. Given the target range of 40 to 60 hours of work per week, should senior management be concerned about the number of hours their employees are currently devoting to work? Explain how the answers to both parts a and b help to answer this question.
Chapter 8 Q#21 Page 348, use data P02_21.xlsx
21. A real estate agent has collected a random sample of 75 houses that were recently sold in a suburban com-munity. She is particularly interested in comparing the appraised value and recent selling price of the houses in this particular market. The data are provided in the file P08_21.xlsx. Using this sample data, calculate a 95% confidence interval for the mean difference between the appraised values and selling prices of the houses sold in this suburban community. Interpret the confidence inter-val for the real estate agent.
Chapter 8 Q#29 Page 358, No Data Required
29. Elected officials in a California city are preparing the annual budget for their community. They would like to estimate how much their constituents living in this city are typically paying each year in real estate taxes. Given that there are over 100,000 homeowners in this city, the officials have decided to sample a representative subset of taxpayers and study their tax payments. a. What sample size is required to generate a 95% con-fidence interval for the mean annual real estate tax payment with a half-length of $100? Assume that the best estimate of the population standard deviation s is $535.
b. If a random sample of the size from part a is selected and a 95% confidence interval for the mean is calculated from this sample, will the half-length of the confidence interval be equal to $100? Explain why or why not.
c. Now suppose that the officials want to construct a 95% confidence interval with a half-length of $75. What sample size is required to achieve this objective? Again, assume that the best estimate of the population standard deviation s is $535. Explain the difference between this result and the result from part a.
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