Assignment task: You are the manager of an accounting firm that monitors the monthly billing hours for accountants at each of your five branch offices. You use control charts for this purpose. If the mean monthly billable hours falls below the LCL, there are apparently some problems with the productivity of that branch. If, on the other hand, the mean monthly billable hours exceeds the UCL, it means that a new branch should possibly be opened in an adjacent neighborhood.
Using 10-day samples for the Oceanfront Branch for each of the six months below, answer the questions that follow. Use control limits of +/- 3 sigma. The average range of the six samples was found to be 16 hours.
Month Average of 10 days of billable hours
January 70
February 75
March 72
April 85
May 69
June 70
What is the UCL?
What is the LCL?