Exam Prep Quality and Statistical Process Control Ch7

Matching Supply with Demand: An Introduction to Operations Management, 4e (Cachon)

Chapter 07 Quality and Statistical Process Control

1) Which of the following identifies the process where a chemist accidentally creates a potentially explosive solution due to miscalculation?

A) Natural Variation

B) Common Cause Variation

C) Assignable Cause Variation

D) Environmental Variable

E) Outcome Variable

Difficulty: 3 Hard

Topic: The Statistical Process Control Framework

AACSB: Analytical Thinking

Blooms: Analyze

2) Sarita works for a busy bakery in downtown Manhattan. She noticed this morning that her large batch of bagels did not rise properly during the time that they were in the oven the way they usually do. With very little time before the shop opens for the morning rush, she decides to study this situation with the statistical process control, or SPC, approach. Which of the following should she do in this particular situation?

A) She should measure the capability of the process in making defects.

B) She should monitor her process to see whether this variation is aligned to the usual pattern or if an assignable cause occurred.

C) If she determines that this is a result of an assignable cause, she should investigate the root cause of the variation.

D) She should try to avoid this from recurring if it was from an assignable cause and possibly utilize a different recipe that is more robust.

E) Based on the information we have so far, Sarita should do all of the above.

Difficulty: 3 Hard

Topic: The Statistical Process Control Framework

AACSB: Reflective Thinking

Blooms: Analyze

3) Which of the following is an outcome variable when studying a set of adult twins?

A) The heights of the adult twins.

B) The average amount of calories that the adult twins consumed as children.

C) The environment that adult twins grew up in.

D) The height of the twins' parents.

E) None of the above.

Difficulty: 3 Hard

Topic: The Statistical Process Control Framework

AACSB: Analytical Thinking

Blooms: Analyze

[The following information applies to questions 4-6.]

Comfort Living Appliances has just released plans for a new flexible, yet light-weight vacuum cleaner. The proprietary component of this device is the pivot function of the handle. The plans have indicated that there remains the possibility of variation within this pivot function. The designers have specified that the height of this section should measure 44.550 mm in height but concede that anywhere between 44.500 and 44.645 is acceptable before the function interferes with the hose extender.

4) What is the lower specification limit (LSL) of this vacuum cleaner's pivot function?

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Knowledge Application

Blooms: Apply

5) What is the tightness of the design specification for the height of the pivot function?

A) 44.645

B) 44.550

C) 0.140

D) 0.145

E) 44.500

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Knowledge Application

Blooms: Apply

6) Let's assume the designers have estimated a standard deviation for the pivot function of 0.019321 and assigned this a six-sigma process. What is the process capability?

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Analytical Thinking

Blooms: Analyze

7) Many organizations aim for alignment within six-sigma program requirements. Which of the following does that include?

A) A minimum process capability index of 1.33.

B) A process capability of 2.0 at every step.

C) A USL that is six standard deviations above the mean.

D) An LSL that is 3 standard deviations below the mean.

E) A process capability of 2.0 at every step and a USL that is six standard deviations above the mean.

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Analytical Thinking

Blooms: Analyze

8) What is the maximum standard deviation allowed for a process to meet the rigorous six-sigma standards?

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Reflective Thinking

Blooms: Analyze

9) A company has an assigned LSL of 39.255mm and a USL of 39.195mm for one of its critical components. The standard deviation of the sample it checks daily is 0.012875 with a sigma of 4.5. What is the process capability index for this component?

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Analytical Thinking

Blooms: Analyze

[The following information applies to questions 10-13.]

An integral component for a large tractor model has a USL of 950 mm and an LSL of 949.90 mm. Assuming this follows a six-sigma process and the standard deviation is 0.0128.

10) What is the process capability score?

A) 1.3881

B) 1.3021

C) 1.3939

D) 1.3722

E) 2.0021

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Analytical Thinking

Blooms: Analyze

11) Based on the capability score for the tractor component above, what is the present defect frequency in ppm?

A) 63.3

B) 26.7

C) 10.8

D) 4.2

E) 1.59

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Knowledge Application

Blooms: Apply

12) Let's say the tractor company who makes the component above would like to reduce their ppm to 26. To what level would they have to reduce the standard deviation to achieve this objective?

Difficulty: 3 Hard

Topic: Capability Analysis

AACSB: Analytical Thinking

Blooms: Analyze

13) When variation in the process is observed to be abnormal, what would this indicate?

Difficulty: 3 Hard

Topic: Conformance Analysis

AACSB: Knowledge Application

Blooms: Apply

[The following information applies to questions 14-17.]

Let's say an operations specialist has measured the estimated standard deviation of all parts for a process to be 0.002921374 for five observation periods. The X-double-bar, or average across averages, is 57.258.

14) What is the estimated standard deviation for this sample of measurements?

Difficulty: 3 Hard

Topic: Conformance Analysis

AACSB: Knowledge Application

Blooms: Apply

15) What is the upper control limit (UCL) for this sample that will keep this process within control?

Difficulty: 3 Hard

Topic: Conformance Analysis

AACSB: Knowledge Application

Blooms: Apply

16) What is the lower control limit (LCL) for this sample that will prevent the sample mean from becoming out of control?

Difficulty: 3 Hard

Topic: Conformance Analysis

AACSB: Knowledge Application

Blooms: Apply

17) A few weeks later, this operations specialist begins to notice a trend in which the daily sample averages are falling just outside the upper and lower control limits. What would this be an indication of?

A) The process is out of control.

B) The process is beyond three standard deviations of the mean.

C) This indicates that an assignable cause has occurred.

D) This pattern justifies the need to investigate further.

E) All of the above statements are correct.

Difficulty: 3 Hard

Topic: Conformance Analysis

AACSB: Reflective Thinking

Blooms: Analyze

18) Ironworks Fence Company picked up on a defect in the way its rails line up on its latest batch of residential fencing. The control chart that it updates periodically has indicated that this is because of an assignable cause variation. What is the first thing that should occur after this observation?

A) Calculate the control limits.

B) Calculate the specification limits.

C) Calculate the defects with binary outcomes.

D) Construct a diagram that analyzes the potential root causes.

E) All of the above.

Difficulty: 3 Hard

Topic: Investigating Assignable Causes

AACSB: Reflective Thinking

Blooms: Analyze

19) Ironworks Fence Company decided to create a p-chart with a large sample size of 200 fence sections to identify the number of defective parts. They find that the average across averages is a defect of 8%. What is the estimated standard deviation of effects for this sample size?

A) 0.0192

B) 0.0183

C) 0.0191

D) 0.0182

E) 0.0121

Difficulty: 3 Hard

Topic: Defects with Binary Outcomes: p-Charts

AACSB: Knowledge Application

Blooms: Apply

20) What is the upper control limit for the percentage of defective parts based on the estimated standard deviation above?

A) 0.1379

B) 0.1372

C) 0.1376

D) 0.1299

E) 0.1400

Difficulty: 3 Hard

Topic: Defects with Binary Outcomes: p-Charts

AACSB: Knowledge Application

Blooms: Apply