Written Assignment

Written Assignment

(Due March 6, 2015)

Submit your solutions to the following problems. Write your solutions clearly and neatly. Show all your work to get credit!

1. (Chapter 5)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 7 (n = 7)customer calls are measured for time. Results from the last six samples are shown in the following table.

Observation (seconds)

Sample

1

2

3

4

5

6

7

1

425

408

422

380

410

401

413

2

410

425

431

427

422

420

400

3

400

416

419

424

423

425

405

4

404

406

395

400

406

390

402

5

395

407

400

402

411

405

407

6

398

417

405

418

402

415

410

a) Management is willing to use three-sigma limits. Use the data and Table 5.1 (page 171) to determine the control limits for an R-chart and an -chart.

b) Plot sample means and ranges on their respective control charts and interpret the results.

2. (Chapter 6)Watch the video for the case “Gate Turnaround at Southwest Airlines” (Page 222) and answer the following two questions. Please reference all outside resources if you use any other than the textbook.

a) What is the key competitive priority of SWA? How does SWA’s strategic capacity decisions support its competitive priority?

b) How would you measure capacity and utilization in the airline industry? Formulate capacity and utilization for the airline industry.

3.

Vacuum

(5 mins)

Wash

(10 mins)

Dry

(6 mins)

(Chapter 7)The figure below shows the flow of a car wash processthat has three stations; vacuum, wash, and dry. The numbers in parentheses are the times in minutes for each step of the process.

Answer parts a, b, and c assuming that a car can advance to the next station as soon as the next station is ready (idle).

a) What is the throughput time to complete a car wash when there are no waiting lines?

b) What is the capacity of the car wash process?

c) How would the capacity of the system change if another wash station is added, i.e. what is the system capacity with two wash stations?

d) Assume the car wash station serves only one car at a time, i.e. the station will not start vacuuming the next car in the line until the one in the system has gone through all three processes (vacuum, wash, and dry). What would be the capacity of the system in this case?

4. (Chapter 7)A company is setting up an assembly line to produce 90 units per hour. The table below identifies the work elements, times, and immediate predecessors.

Work Element

Time (Sec.)

Immediate Predecessor(s)

A

35

B

20

A

C

30

B

D

23

C

E

28

D

F

15

B

G

17

F

H

15

F

I

12

G,H

J

23

E,I

a) What cycle time is required to satisfy the required output?

b) What is the theoretical minimum number of stations?

c) Use one of the heuristic decision rules described in Table 7.3 on page 258 to balance the assembly line so that it will produce 90 units per hour. Clearly state which decision rule you are using and the work elements assigned to each station.

d) What is the efficiency of the line you found in part c?

5. (Chapter 8)Watch the video for the case “Lean Systems at Autoliv” (page 303) and describe, in about one page, the JIT considerations presented in the chapter as they relate Autoliv’s manufacturing environment.

6. (Chapter 14) Observed monthly sales of a popular brand tennis shoe at a medium-sized sports store at the town’s mall over the first eight months of the year are given in the following table.

Month

Jan

Feb

Mar

Apr

May

June

July

Aug

Demand

27

32

30

45

38

40

43

46

a) Use a three-month moving average method to forecast the sales for the months April through September. Also compute the mean squared error (MSE) based on the sales and forecasts for months April through August.

b) If the forecast for January was 25, determine the forecast for sales for the months February through September using an exponential smoothing method witha = 0.40. Also compute the mean squared error (MSE) based on the sales and forecasts for months April through August.

c) Which method would you recommend based on MSE? Why?

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