# 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?

Please explain your solutions clearly.

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)