TBChap 010-1 - Chap 10 test questions PDF

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Chapter 10 Quality Control

True / False Questions 1. Approving the effort that occurs during the production process is known as acceptance sampling. True

False

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

False

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

False

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

False

5. Processes that are in control eliminate variations. True

False

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

False

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

False

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

False

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

False

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

False

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

False

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

False

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

False

14. 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

False

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

False

16. Concluding that a process is out of control when it is not is known as a Type I error. True

False

17. An R value of zero (on a range chart) means that the process must be in control since all sample values are equal. True

False

18. Range charts are used mainly with attribute data. True

False

19. Range charts and p-charts are both used for variable data. True

False

20. A p-chart is used to monitor the fraction of defectives in the output of a process. True

False

21. A c-chart is used to monitor the total number of defectives in the output of a process. True

False

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22. A c-chart is used to monitor the number of defects per unit for process output. True

False

23. Tolerances represent the control limits we use on the charts. True

False

24. Process capability compares process variability to the tolerances. True

False

25. Control limits used on process control charts are specifications established by design or customers. True

False

26. Control limits tend to be wider for more variable processes. True

False

27. Patterns of data on a control chart suggest that the process may have nonrandom variation. True

False

28. The output of a process may not conform to specifications even though the process may be statistically "in control." True

False

29. Run tests are useful in helping to identify nonrandom variations in a process. True

False

30. Run tests give managers an alternative to control charts; they are quicker and cost less. True

False

31. Statistical process control focuses on the acceptability of process output. True

False

32. A run test checks a sequence of observations for randomness. True

False

33. Cpk is useful even when the process is not centered. True

False

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34. The process capability index (indicated by Cpk) can be used only when the process is centered. True

False

35. Quality control is making sure that processes are performing in an acceptable manner. True

False

36. The primary purpose of statistical process control is to detect a defective product before it is shipped to a customer. True

False

37. The Taguchi loss function suggests that the capability ratio can be improved by extending the spread between LCL and UCL. True

False

38. The variation of a sampling distribution is tighter than the variation of the underlying process distribution. True

False

39. The sampling distribution can be assumed to be approximately normal even when the underlying process distribution is not normally distributed. True

False

40. Approximately 99.7 percent of sample means will fall within plus or minus two standard deviations of the process mean if the process is under control. True

False

41. The best way to assure quality is to use extensive inspection and control charts. True

False

42. Control limits are based on multiples of the process standard deviation. True

False

43. Attribute data are counted, variable data are measured. True

False

44. The number of defective parts in a sample is an example of variable data because it will "vary" from one sample to another. True

False

45. Larger samples will require wider x-bar control limits because there is more data. True

False

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46. When a process is not centered, its capability is measured in a slightly different way. The symbol for this case is Cpk. True

False

47. Range control charts are used to monitor process central tendency. True

False

Multiple Choice Questions 48. 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. 49. 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. insourcin g. B. inspectio n. C. outsourcin g. D. acceptance sampling. E. capability assessment.

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50. 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. 51. The assurance that processes are performing in an acceptable manner is the focus of:

A. variability analysis. B. quality assurance. C. capability assessment. D. quality control. E. acceptance sampling. 52. Inspection is a(n):

A. preventio n. B. contro l. C. monitorin g. D. correctiv e. E. appraisa l.

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53. 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 54. 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 55. The greater the volume of the process being targeted for inspection, the more attractive __________ inspection is.

A. monitor ed B. controll ed C. periodi c D. variabl e E. automat ed

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56. Which of the following quality control sample statistics indicates a quality characteristic that is an attribute?

A. mea n B. varianc e C. standard deviation D. rang e E. proporti on 57. 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. 58. A control chart used to monitor the process mean is the:

A. pchart. B. Rchart. C. x-bar chart. D. cchart. E. Gantt chart.

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59. A control chart used to monitor the fraction of defectives generated by a process is the:

A. pchart. B. Rchart. C. x-bar chart. D. cchart. E. Gantt chart. 60. 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. 61. A c-chart is used for:

A. mean s. B. range s. C. percent defective. D. fraction defective per unit. E. number of defects per unit.

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62. A control chart used to monitor the number of defects per unit is the:

A. pchart. B. Rchart. C. x-bar chart. D. cchart. E. Gantt chart. 63. 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-thanaverage 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. 64. If a process is performing as it should, it is still possible to obtain observations which are outside of which limits? (I) tolerances (II) control limits (III) process variability

A. I B. I I C. I and II D. II and III E. I, II, and III

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65. 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 66. 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. 67. 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

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68. _______ variation is a variation whose cause can be identified.

A. Assignabl e B. Controllab le C. Rando m D. Statistic al E. Theoretic al 69. 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 70. A shift in the process mean for a measured characteristic would most likely be detected by a:

A. pchart. B. x-bar chart. C. cchart. D. Rchart. E. schart.

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71. The range chart (R-chart) is most likely to detect a change in:

A. proportio n. B. mea n. C. number defective. D. variabilit y. E. sample size. 72. 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. 73. 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.

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74. 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 75. A time-ordered plot of sample statistics is called a(n) ______ chart.

A. statistic al B. inspecti on C. contr ol D. sim o E. lim it 76. Consider the following information:

The number of runs up and down for the preceding data is:

A. 3 . B. 4 . C. 5 . D. 6 . E. none of these.

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77. Consider the following information:

The number of runs with respect to the sample median is:

A. 3 . B. 4 . C. 5 . D. 6 . E. none of these. 78. The following data occurs chronologically from left to right:

The number of runs with respect to the sample median is:

A. 2 . B. 3 . C. 4 . D. 5 . E. none of these.

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79. The following data occurs chronologically from left to right:

The number of runs up and down is:

A. 2 . B. 3 . C. 4 . D. 5 . E. none of these. 80. A design engineer wants to construct a sample mean chart for controlling the service life of a halogen headlamp his company produces. He knows from numerous previous samples that this service life is normally distributed with a mean of 500 hours and a standard deviation of 20 hours. On three recent production batches, he tested service life on random samples of four headlamps, with these results:

What is the sample mean service life for sample 2?

A. 460 hours B. 495 hours C. 500 hours D. 515 hours E. 525 hours

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