67.How do you explain the difference between the results obtained in Questions 65and 66?
68.Compute (2.0),P Zwhere Zis a standard normal random variable.
69.Compare the results of Question 68 to the results obtained in Questions 65 and 66.How do you explain the difference in these probabilities?
QUESTIONS 70 THROUGH 72 ARE BASED ON THE FOLLOWING INFORMATION:Senior management of a consulting services firm is concerned about a growing decline inthe firm’s weekly number of billable hours. The firm expects each professional employeeto spend at least 40 hours per week on work. In an effort to understand this problembetter, management would like to estimate the standard deviation of the number of hourstheir employees spend on work-related activities in a typical week. Rather thanreviewing the records of all the firm’s full-time employees, the management randomlyselected a sample of size 50 from the available frame. The sample mean and samplestandard deviations were 48.5 and 7.5 hours, respectively. 70.Construct a 99% confidence interval for the standard deviation of the number ofhours this firm’s employees spend on work-related activities in a typical week.