Chapter 10 Quality Control Operations Management 12e Stevenson

A c-chart is used for: A. means. B. ranges. C. percent defective. D. fraction defective per unit. E. number of defects per unit.

E. number of defects per unit.

A lower control limit must by definition be a value less than an upper control limit.

True

High-cost, low-volume items often require careful inspection since we make them so infrequently.

True

If a point on a control chart falls outside one of the control limits, this suggests that the process output is nonrandom and should be investigated.

True

The amount of inspection needed is governed by the costs of inspection and the expected costs of passing defective items.

True

The amount of inspection we choose can range from no inspection at all to inspecting each item numerous times.

True

The optimum level of inspection minimizes the sum of inspection costs and the cost of passing defectives.

True

Acceptance sampling, when it is used, is used: (I) before production. (II) during production. (III) after production. A. I only B. I and III only C. I and II only D. II and III only E. I, II, and III

B. I and III only Acceptance sampling is used to assess inputs to and outputs from a process.

The more effective and all-encompassing a firm's quality control and continuous improvement efforts, the less that company will need to rely on: A. insourcing. B. inspection. C. outsourcing. D. acceptance sampling. E. capability assessment.

B. inspection. The best companies emphasize designing quality into the process, thereby greatly reducing the need for inspection.

_______ variation is a variation whose cause can be identified. A. Assignable B. Controllable C. Random D. Statistical E. Theoretical

A. Assignable Assignable variation has a special cause.

Quality control, in contrast to quality assurance, is implemented: A. during production. B. by top management. C. after production. D. by self-directed teams. E. before inspection.

A. during production. Quality control is used to monitor processes during production; quality assurance is used to evaluate processes' outputs.

A control chart used to monitor the fraction of defectives generated by a process is the: A. p-chart. B. R-chart. C. x-bar chart. D. c-chart. E. Gantt chart.

A. p-chart. The p-chart monitors the fraction defective.

A shift in the process mean for a measured characteristic would most likely be detected by a: A. p-chart. B. x-bar chart. C. c-chart. D. R-chart. E. s-chart.

B. x-bar chart. x-bar charts monitor the process mean.

Which of the following is not a step in the quality control process? A. Define what is to be controlled. B. Compare measurements to a standard. C. Eliminate each of the defects as they are identified. D. Take corrective action if necessary. E. Evaluate corrective action.

C. Eliminate each of the defects as they are identified.

A plot below the lower control limit on the range chart: (I) should be ignored since lower variation is desirable. (II) may be an indication that process variation has decreased. (III) should be investigated for assignable cause. A. I and II B. I and III C. II and III D. II only E. I, II, and III

C. II and III Plots outside of control limits should be investigated.

Which of the following relationships must always be incorrect? A. Tolerances > process variability > control limits B. Process variability > tolerances > control limits C. Tolerances > control limits > process variability D. Process variability > control limits > tolerances E. Process variability < tolerances < control limits

C. Tolerances > control limits > process variability Process variability will always be greater than control limits.

Quality control tools are not really used to fix quality so much as they are used to: A. highlight when processes are not capable. B. point out when random variation is present. C. alert when corrective action is needed. D. monitor the quality of incoming shipments or outgoing finished goods. E. initiate team-building exercises.

C. alert when corrective action is needed. Quality control tools are needed to decide when corrective action is needed.

A time-ordered plot of sample statistics is called a(n) ______ chart. A. statistical B. inspection C. control D. simo E. limit

C. control

A time-ordered plot of representative sample statistics is called a(n): A. Gantt chart. B. simo chart. C. control chart. D. up-down matrix. E. standard deviation table.

C. control chart. Control charts are time-ordered plots of sample statistics.

A point which is outside of the lower control limit on an R-chart: A. is an indication that no cause of variation is present. B. should be ignored because it signifies better-than-average quality. C. should be investigated because an assignable cause of variation might be present. D. should be ignored unless another point is outside that limit. E. is impossible since the lower limit is always zero.

C. should be investigated because an assignable cause of variation might be present. Points outside of the control limits should be investigated as signals of nonrandom variation being present.

The process capability index (Cpk) may mislead if: (I) the process is not stable. (II) the process output is not normally distributed. (III) the process is not centered. A. I and II B. I and III C. II and III D. II only E. I, II, and III

E. I, II, and III

The amount of inspection needed depends on __________ and __________. A. the amount of automation; the reliability of inspectors B. the quality of the supplier; the target market of the process C. the costs of inspection; the costs of passing on defective items D. where in the process the inspection occurs; the volume of the process E. the cost of the item being inspected; the use of the item being inspected

C. the costs of inspection; the costs of passing on defective items The amount of inspection needed is governed by the costs of inspection and the expected costs of passing defective items.

A p-chart would be used to monitor: A. average shrinkage. B. dispersion in sample data. C. the fraction defective. D. the number of defects per unit. E. the range of values.

C. the fraction defective.

A control chart used to monitor the process mean is the: A. p-chart. B. R-chart. C. x-bar chart. D. c-chart. E. Gantt chart.

C. x-bar chart. The x-bar chart monitors the process mean.

The probability of concluding that assignable variation exists when only random variation is present is: (I) the probability of a Type I error. (II) known as the alpha risk. (III) highly unlikely. (IV) the sum of probabilities in the two tails of the normal distribution. A. I and II B. I and IV C. II and III D. I, II, and IV E. I, III, and IV

D. I, II, and IV Incorrect signals can be on either side of the distribution.

A control chart used to monitor the number of defects per unit is the: A. p-chart. B. R-chart. C. x-bar chart. D. c-chart. E. Gantt chart.

D. c-chart.

The purpose of control charts is to: A. estimate the proportion of output that is acceptable. B. weed out defective items. C. determine if the output is within tolerances/specifications. D. distinguish between random variation and assignable variation in the process. E. provide meaningful work for quality inspectors.

D. distinguish between random variation and assignable variation in the process.

The optimum level of inspection is where the: A. cost of inspection is minimum. B. cost of passing defectives is minimum. C. total cost of inspection and defectives is maximum. D. total cost of inspection and defectives is minimum. E. difference between inspection and defectives costs is minimum.

D. total cost of inspection and defectives is minimum.

The range chart (R-chart) is most likely to detect a change in: A. proportion. B. mean. C. number defective. D. variability. E. sample size.

D. variability. The range chart monitors variability.

Inspection is a(n): A. prevention. B. control. C. monitoring. D. corrective. E. appraisal.

E. appraisal

An x-bar control chart can only be valid if the underlying population it measures is a normal distribution.

FALSE The sample average typically is normally distributed regardless of the underlying distribution of the process.

A process that exhibits random variability would be judged to be out of control.

False

Approving the effort that occurs during the production process is known as acceptance sampling.

False

Attributes need to be measured, whereas variable data can be counted.

False

Low-cost, high-volume items often require more intensive inspection than other types of items.

False

Processes that are in control eliminate variations.

False

Statistical process control is the measurement of rejects in the final product.

False

The optimum level of inspection occurs when we catch at least 98.6 percent of the defects.

False

The purpose of statistical process control is to ensure that historical output is random.

False