solved proplem+ case - Confirming Pages 824 Chapter Eighteen Management of Waiting Lines The basic relationship formulas can be used with an infinite

# solved proplem+ case - Confirming Pages 824 Chapter...

This preview shows page 1 - 2 out of 8 pages.

SOLVED PROBLEMS 824 Chapter Eighteen Management of Waiting Lines KEY POINTS 1. Waiting line occur because there is an imbalance between supply and demand in service systems. 2. One cause of imbalances is variability in service times and/or customer arrival times. 3. Two important approaches to managing waiting lines are reducing variability where possible by standardizing a process and/or altering the perceived waiting time. channel, 797 finite-source situation, 797 infinite-source situation, 796 multiple-priority model, 812 queue discipline, 800 queuing theory, 794 KEY TERMS Use this approach for infinite-source problems: 1. Note the number of servers. If there is only one server, M 1. Use the basic relationship formulas in Figure 18.7 and the single-server formulas in Table 18.1. If service is constant, use Formula 18–9 for L q . For M > 1, use the basic relationship formulas in Figure 18.7, the multiple-server values in Table 18.4 for L q and P 0 , and Formulas 18–12 and 18–13. 2. Determine the customer arrival rate and the service rate. If the arrival or service time is given instead of a rate, convert the time to a rate. For example, a service time of 10 minutes would con- vert to a service rate, , of [1/(10 minutes/customer)] (60 minutes/hour) 6 customers/hour 3. If multiple priorities are involved, use the Excel template on the Web site (preferred approach) or the formulas in Table 18.5. Problem 1 Infinite source. One of the features of a new machine shop will be a well-stocked tool crib. The manager of the shop must decide on the number of attendants needed to staff the crib. Attendants will receive \$9 per hour in salary and fringe benefits. Mechanics’ time will be worth \$30 per hour, which includes salary and fringe benefits plus lost work time caused by waiting for parts. Based on previous experience, the manager estimates requests for parts will average 18 per hour with a ser- vice capacity of 20 requests per hour per attendant. How many attendants should be on duty if the manager is willing to assume that arrival and service rates will be Poisson-distributed? (Assume the number of mechanics is very large, so an infinite-source model is appropriate.) Solution The basic relationship formulas can be used with an infinite source model. There are formulas for system utilization, the average number or average time waiting for service, the average number being served, and the average number or time in the system. Refer to Figure 18.7 on p. 802 to help you connect with the appropriate formula. The formulas are on p. 802. Single-channel model: Use when there is one server, team, or crew. See p. 803. Single-channel, constant service time. See p. 804. Multiple-channel model. Use when there are two or more independent servers, teams, or crews. See p. 805 Multiple-priority model. Use when service order is based on priority class. See p. 813.

#### You've reached the end of your free preview.

Want to read all 8 pages?

• Fall '16
• average number, average waiting time, Jeris J. White

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern