# operations management

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A critical dimension of the service quality of a call center is the wait time of a caller to get to a sales representative. Periodically, random samples of 6 customer calls are measured for time. Results from the last five samples are shown in the table.
Observation (seconds)
Sample
1
2
3
4
5
6
1
435
408
422
436
410
401
2
440
410
431
427
422
430
3
400
426
419
424
433
425
4
411
406
395
442
436
410
5
408
407
407
435
411
405
a) Management is willing to use three-sigma limits. Using the factors in Table 5.1, determine upper and lower limits for mean and range charts.
b) Plot sample means and ranges on their respective control charts. Is the process in control?
2. (Chapter 6) Larry’s Wickets, Inc. is producing two types of products: A and B. Both are produced at the same machining operation. The machines operate on two 8-hour shifts, 5 days per week, and 50 weeks per year. The manager wants to maintain a 20 percent capacity cushion. Because of demand uncertainties, the operations manager obtained three demand forecasts (pessimistic, expected, and optimistic). The demand forecasts, lot sizes, processing times, and setup times are given in the below table. Determine the minimum, expected, and maximum number of machines needed.
Time Standards
Demand Forecast
Product
Processing (hr/unit)
Setup (hr/lot)
Lot Size (units/lot)
Pessimistic
Expected
Optimistic
A
0.30
1
200
100,000
120,000
150,000
B
0.25
2
100
190,000
210,000
230,000
3. (Chapter 7) The figure below shows the process for paying tuition at a major university. Students are provided their bill for the next term for review, and then routed to different tables for questions to be answered before finally paying their tuition at E. The numbers in parentheses are the times in minutes for each step of the process.
a) What is the capacity for the A-B-C-E process route?
b) What is the capacity for the A-B-D-E process route?
c) If 60% of the students are routed to C and 40% are routed to D, what is the average capacity per hour for the process?
d) Where would you expect student wait times to occur? Why?
4. (Chapter 15) Complete the MPS record in Figure 15.27 on page 569 of your textbook. Explain how you determined projected on-hand inventory, MPS quantity, and MPS start.
A
(2)
C
(6)
D
(10)
E
(4)
B
(5)

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