Operations management final exam questions and answers

4.

For each of the accompanying control charts, analyze the data using both median and up/down run tests with z = ± 1.96 limits.

a.

Are nonrandom variations present? Assume the center line is the long-term median.

Picture

Test

Conclusion

Median

Up/Down

b.

Are nonrandom variations present? Assume the center line is the long-term median.

Picture

Test

Conclusion

Median

Up/Down

5.

A company has just negotiated a contract to produce a part for another firm. In the process of manufacturing the part, the inside diameter of successive parts becomes smaller and smaller as the cutting tool wears. However, the specs are so wide relative to machine capabilities that it is possible to set the diameter initially at a large value and let the process run for a while before replacing the cutting tool.

The inside diameter decreases at an average rate of .001 cm per part, and the process has a standard deviation of .05 cm. The variability is approximately normal. Assuming a three-sigma buffer at each end, how frequently must the tool be replaced if the process specs are 3 cm and 3.5 cm. Use (Number of shafts) n = 1.

Picture

Determine how many pieces can be produced before the LCL just crosses the lower tolerance of 3 cm. (Do not round your intermediate calculations.)

After [removed]pieces the cutting tool should be replaced.

6.

A production process consists of a three-step operation. The scrap rate is 10 percent for the first step and 6 percent for the other two steps.

a.

If the desired daily output is 450 units, how many units must be started to allow for loss due to scrap? (Do not round intermediate calculations. Round up your final answer to the next whole number.)

Number of units

[removed]

b.

If the scrap rate for each step could be cut in half at every operation, how many units would this save in terms of the scrap allowance? (Do not round intermediate calculations. Round up your final answer to the next whole number.)

Number of units

[removed]

c.

If the scrap represents a cost of $10 per unit, how much is it costing the company per day for the original scrap rate (i.e. the Part a scrap rate)? (Round your answer to the nearest whole number. Omit the "$" sign in your response.)

Cost

$ [removed]

12.

Use the assignment method to obtain a plan that will minimize the processing costs in the following table under these conditions:

WORKER

A

B

C

D

E

1

14

18

20

17

18

2

14

15

19

16

17

Job

3

12

16

15

14

17

4

11

13

14

12

14

5

10

16

15

14

13