- CHAPTER 6: MANAGING QUALITY
- TRUE/FALSE
- 1. Managers at Arnold Palmer Hospital take quality so seriously that the hospital typically is a national leader in several quality areas—so that continuous improvement is no longer necessary.
- False (Global company profile, moderate)
- 2. An improvement in quality must necessarily increase costs.
- False (Quality and strategy, easy)
- 3. For most, if not all organizations, quality is a tactical rather than a strategic issue.
- False (Quality and strategy, moderate)
- 4. The definition of quality adopted by The American Society for Quality is a customer-oriented definition.
- True (Defining quality, easy)
- 5. Conforming to standards is the focus of the product-based definition of quality.
- False (Defining quality, moderate)
- 6. Internal failure costs are associated with scrap, rework, and downtime.
- True (Defining quality, easy)
- 7. Philip Crosby is credited with both of these quality catch-phrases: "quality is free" and "zero defects."
- True (Defining quality, easy)
- 8. Deming's writings on quality tend to focus on the customer and on fitness for use, unlike Juran's work that is oriented toward meeting specifications.
- False (defining quality, moderate)
- 9. Improved quality can increase profitability via flexible pricing.
- True (Defining quality, moderate)
- 10. ISO 9000 has evolved from a set of quality assurance standards toward a quality management system.
- True (International quality standards, moderate)
- 11. Quality is mostly the business of the quality control staff, not ordinary employees.
- False (Total quality management, moderate)
- 12. TQM is important because quality influences all of the ten decisions made by operations managers.
- True (Total quality management, moderate)
- 13. The phrase Six Sigma has two meanings. One is statistical, referring to an extremely high process capability; the other is a comprehensive system for achieving and sustaining business success.
- True (Quality and strategy, moderate)
- 14. Continuous improvement is based on the philosophy that any aspect of an organization can be improved.
- True (Total quality management, moderate)
- 15. Kaizen is similar to TQM in that both are focused on continuous improvement.
- True (Total quality management, moderate)
- 16. The Japanese use the term "poka-yoke" to refer to continuous improvement.
- False (Total quality management, moderate) {AACSB: Multiculture and Diversity}
- 17. Quality circles empower employees to improve productivity by finding solutions to work-related problems in their work area.
- True (Total quality management, moderate) {AACSB: Communication}
- 18. Benchmarking requires the comparison of your firm to other organizations; it is not appropriate to benchmark by comparing one of your divisions to another of your divisions.
- False (Total quality management, moderate)
- 19. Line employees need the knowledge of TQM tools.
- True (Total quality management, easy)
- 20. One of the ways that Just-In-Time (or JIT) influences quality is that by reducing inventory, bad quality is exposed.
- True (Total quality management, moderate)
- 21. The quality loss function indicates that costs related to poor quality are low as long as the product is within acceptable specification limits.
- False (Total quality management, moderate)
- 22. Pareto charts are a graphical way of identifying the few critical items from the many less important ones.
- True (Tools of TQM, moderate)
- 23. A cause-and-effect diagram helps identify the source of a problem.
- True (Tools of TQM, moderate)
- 24. Source inspection is inferior to inspection before costly operations.
- False (The role of inspection, moderate)
- 25. Of the several determinants of service quality, access is the one that relates to keeping customers informed in language they can understand.
- False (TQM in services, moderate)
- 26. High-quality products and services are the most profitable.
- True (Defining quality, easy)
- MULTIPLE CHOICE
- 27. Which of the following statements regarding Arnold Palmer Hospital is false?
- 1. a. The hospital uses a wide range of quality management techniques.
- 2. b. The culture of quality at the hospital includes employees at all levels.
- 3. c. The hospital scores very highly in national studies of patient satisfaction.
- 4. d. The hospital's high quality is measured by low readmission rates, not patient satisfaction.
- 5. e. The design of patient rooms, even wall colors, reflects the hospital's culture of quality.
- d (Global company profile, moderate)
- 28. Arnold Palmer Hospital uses which of the following quality management techniques?
- 1. a. Pareto charts
- 2. b. flow charts
- 3. c. benchmarking
- 4. d. Just-in-Time
- 5. e. The hospital uses all of the above techniques.
- e (Global company profile, easy)
- 29. Which of the following statements best describes the relationship between quality management and product strategy?
- 1. a. Product strategy is set by top management; quality management is an independent activity.
- 2. b. Quality management is important to the low-cost product strategy, but not to the response or differentiation strategies.
- 3. c. High quality is important to all three strategies, but it is not a critical success factor.
- 4. d. Managing quality helps build successful product strategies.
- 5. e. Companies with the highest measures of quality were no more productive than other firms.
- d (Defining quality, moderate)
- 30. "Quality is defined by the customer" is
- 1. a. an unrealistic definition of quality
- 2. b. a user-based definition of quality
- 3. c. a manufacturing-based definition of quality
- 4. d. a product-based definition of quality
- 5. e. the definition proposed by the American Society for Quality
- b (Defining quality, moderate)
- 31. "Making it right the first time" is
- 1. a. an unrealistic definition of quality
- 2. b. a user-based definition of quality
- 3. c. a manufacturing-based definition of quality
- 4. d. a product-based definition of quality
- 5. e. the definition proposed by the American Society for Quality
- c (Defining quality, moderate)
- 32. Three broad categories of definitions of quality are
- 1. a. product quality, service quality, and organizational quality
- 2. b. user-based, manufacturing-based, and product-based
- 3. c. internal, external, and prevention
- 4. d. low-cost, response, and differentiation
- 5. e. Pareto, Shewhart, and Deming
- b (Defining quality, easy)
- 33. According to the manufacturing-based definition of quality,
- 1. a. quality is the degree of excellence at an acceptable price and the control of variability at an acceptable cost
- 2. b. quality depends on how well the product fits patterns of consumer preferences
- 3. c. even though quality cannot be defined, you know what it is
- 4. d. quality is the degree to which a specific product conforms to standards
- 5. e. quality lies in the eyes of the beholder
- d (Defining quality, moderate)
- 34. The role of quality in limiting a firm's product liability is illustrated by
- 1. a. ensuring that contaminated products such as impure foods do not reach customers
- 2. b. ensuring that products meet standards such as those of the Consumer Product Safety Act
- 3. c. designing safe products to limit possible harm to consumers
- 4. d. using processes that make products as safe or as durable as their design specifications call for
- 5. e. All of the above are valid.
- e (Defining quality, easy) {AACSB: Ethical Reasoning}
- 35. Which of the following is not one of the major categories of costs associated with quality?
- 1. a. prevention costs
- 2. b. appraisal costs
- 3. c. internal failures
- 4. d. external failures
- 5. e. none of the above; they are all major categories of costs associated with quality
- e (Defining quality, moderate)
- 36. All of the following costs are likely to decrease as a result of better quality except
- 1. a. customer dissatisfaction costs
- 2. b. inspection costs
- 3. c. scrap costs
- 4. d. warranty and service costs
- 5. e. maintenance costs
- e (Defining quality, moderate)
- 37. Which of the following statements is not true?
- 1. a. Self-promotion is not a substitute for quality products.
- 2. b. Inferior products harm a firm’s profitability and a nation’s balance of payments.
- 3. c. Product liability transfers from the manufacturer to the retailer once the retailer accepts delivery of the product.
- 4. d. Quality—be it good or bad—will show up in perceptions about a firm’s new products, employment practices, and supplier relations.
- 5. e. Legislation such as the Consumer Product Safety Act sets and enforces product standards by banning products that do not reach those standards.
- c (Defining quality, moderate)
- 38. "Employees cannot produce goods that on average exceed the quality of what the process is capable of producing" expresses a basic element in the writings of
- 1. a. Vilfredo Pareto
- 2. b. Armand Feigenbaum
- 3. c. Joseph M. Juran
- 4. d. W. Edwards Deming
- 5. e. Philip B. Crosby
- d (Defining quality, moderate)
- 39. "Quality Is Free," meaning that the costs of poor quality have been understated, is the work of
- 1. a. W. Edwards Deming
- 2. b. Joseph M. Juran
- 3. c. Philip B. Crosby
- 4. d. Crosby, Stills, and Nash
- 5. e. Armand Feigenbaum
- c (Defining quality, moderate)
- 40. The philosophy of zero defects is
- 1. a. the result of Deming's research
- 2. b. unrealistic
- 3. c. prohibitively costly
- 4. d. an ultimate goal; in practice, 1 to 2% defects is acceptable
- 5. e. consistent with the commitment to continuous improvement
- e (Total quality management, moderate)
- 41. Based on his 14 Points, Deming is a strong proponent of
- 1. a. inspection at the end of the production process
- 2. b. an increase in numerical quotas to boost productivity
- 3. c. looking for the cheapest supplier
- 4. d. training and knowledge
- 5. e. all of the above
- d (Total quality management, moderate)
- 42. Stakeholders who are affected by the production and marketing of poor quality products include
- 1. a. stockholders, employees, and customers
- 2. b. suppliers and creditors, but not distributors
- 3. c. only stockholders, creditors, and owners
- 4. d. suppliers and distributors, but not customers
- 5. e. only stockholders and organizational executives and managers
- a (Defining quality, moderate) {AACSB: Ethical Reasoning}
- 43. Regarding the quality of design, production, and distribution of products, an ethical requirement for management is to
- 1. a. determine whether any of the organization's stakeholders are violated by poor quality products
- 2. b. gain ISO 14000 certification for the organization
- 3. c. obtain a product safety certificate from the Consumer Product Safety Commission
- 4. d. have the organization's legal staff write disclaimers in the product instruction booklets
- 5. e. compare the cost of product liability to the external failure cost
- a (Defining quality, moderate) {AACSB: Ethical Reasoning}
- 44. If 1 million passengers pass through the St. Louis Airport with checked baggage each month, a successful Six Sigma program for baggage handling would result in how many passengers with misplaced luggage?
- 1. a. 3.4
- 2. b. 6.0
- 3. c. 34
- 4. d. 2700
- 5. e. 6 times the monthly standard deviation of passengers
- a (Total quality management, moderate) {AACSB: Analytic Skills}
- 45. Which of the following is true about ISO 14000 certification?
- 1. a. It is not a prerequisite for ISO 9000 certification.
- 2. b. It deals with environmental management.
- 3. c. It offers a good systematic approach to pollution prevention.
- 4. d. One of its core elements is life-cycle assessment.
- 5. e. All of the above are true.
- e (International quality standards, moderate)
- 46. Suppose that a firm has historically been achieving “three-sigma” quality. If the firm later changes its quality management practices such that begins to achieve “six-sigma” quality, which of the following phenomena will result?
- 1. a. The average number of defects will be cut in half.
- 2. b. The specification limits will be moved twice as far from the mean.
- 3. c. The average number of defects will be cut by 99.9997%.
- 4. d. The average number of defects will be cut by 99.87%.
- 5. e. The average number of defects will be cut by 99.73%.
- d (Total quality management, difficult) {AACSB: Analytic Skills}
- 47. To become ISO 9000 certified, organizations must
- 1. a. document quality procedures
- 2. b. have an onsite assessment
- 3. c. have an ongoing series of audits of their products or service
- 4. d. all of the above
- 5. e. none of the above
- d (International quality standards, moderate)
- 48. Total quality management emphasizes
- 1. a. the responsibility of the quality control staff to identify and solve all quality-related problems
- 2. b. a commitment to quality that goes beyond internal company issues to suppliers and customers
- 3. c. a system where strong managers are the only decision makers
- 4. d. a process where mostly statisticians get involved
- 5. e. ISO 14000 certification
- b (Total quality management, moderate)
- 49. A successful TQM program incorporates all of the following except
- 1. a. continuous improvement
- 2. b. employee involvement
- 3. c. benchmarking
- 4. d. centralized decision-making authority
- 5. e. none of the above; a successful TQM program incorporates all of the above
- d (Total quality management, moderate)
- 50. "Kaizen" is a Japanese term meaning
- 1. a. a foolproof mechanism
- 2. b. just-in-time (JIT)
- 3. c. a fishbone diagram
- 4. d. setting standards
- 5. e. continuous improvement
- e (Total quality management, easy) {AACSB: Multiculture and Diversity}
- 51. Which of the following statements regarding "Six Sigma" is true?
- 1. a. The term has two distinct meanings—one is statistical; the other is a comprehensive quality system.
- 2. b. Six Sigma means that about 94 percent of a firm's output is free of defects.
- 3. c. The Six Sigma program was developed by Toyota in the 1970's.
- 4. d. The Six Sigma program is for manufacturing firms, and is not applicable to services.
- 5. e. Six Sigma certification is granted by the International Standards Organization (ISO).
- a (Total quality management, moderate)
- 52. Quality circles members are
- 1. a. paid according to their contribution to quality
- 2. b. external consultants designed to provide training in the use of quality tools
- 3. c. always machine operators
- 4. d. all trained to be facilitators
- 5. e. none of the above; all of the statements are false
- e (Total quality management, moderate)
- 53. Techniques for building employee empowerment include
- 1. a. building communication networks that include employees
- 2. b. developing open, supportive supervisors
- 3. c. moving responsibility from both managers and staff to production employees
- 4. d. building high-morale organizations
- 5. e. All of the above are techniques for employee empowerment.
- e (Total quality management, moderate)
- 54. Building high-morale organizations and building communication networks that include employees are both elements of
- 1. a. ISO 9000 certification
- 2. b. Six Sigma certification
- 3. c. employee empowerment
- 4. d. Taguchi methods
- 5. e. the tools of TQM
- c (Total quality management, moderate) {AACSB: Communication}
- 55. The process of identifying other organizations that are best at some facet of your operations and then modeling your organization after them is known as
- 1. a. continuous improvement
- 2. b. employee empowerment
- 3. c. benchmarking
- 4. d. copycatting
- 5. e. patent infringement
- c (Total quality management, moderate)
- 56. ISO 9000 seeks standardization in terms of
- 1. a. products
- 2. b. production procedures
- 3. c. suppliers' specifications
- 4. d. procedures to manage quality
- 5. e. all of the above
- d (International quality standards, moderate)
- 57. Costs of dissatisfaction, repair costs, and warranty costs are elements of cost in the
- 1. a. Taguchi Loss Function
- 2. b. Pareto chart
- 3. c. ISO 9000 Quality Cost Calculator
- 4. d. process chart
- 5. e. none of the above
- a (Total quality management, moderate)
- 58. A quality loss function includes all of the following costs except
- 1. a. the cost of scrap and repair
- 2. b. the cost of customer dissatisfaction
- 3. c. inspection, warranty, and service costs
- 4. d. sales costs
- 5. e. costs to society
- d (Tools of TQM, moderate)
- 59. Pareto charts are used to
- 1. a. identify inspection points in a process
- 2. b. outline production schedules
- 3. c. organize errors, problems, or defects
- 4. d. show material flow
- 5. e. all of the above
- c (Tools of TQM, moderate)
- 60. The "four Ms" of cause-and-effect diagrams are
- 1. a. material, machinery/equipment, manpower, and methods
- 2. b. material, methods, men, and mental attitude
- 3. c. named after four quality experts
- 4. d. material, management, manpower, and motivation
- 5. e. none of the above
- a (Tools of TQM, moderate)
- 61. Among the tools of TQM, the tool ordinarily used to aid in understanding the sequence of events through which a product travels is a
- 1. a. Pareto chart
- 2. b. process chart
- 3. c. check sheet
- 4. d. Taguchi map
- 5. e. poka-yoke
- b (Tools of TQM, moderate)
- 62. The process improvement technique that sorts the "vital few" from the "trivial many" is
- 1. a. Taguchi analysis
- 2. b. Pareto analysis
- 3. c. benchmarking
- 4. d. Deming analysis
- 5. e. Yamaguchi analysis
- b (Tools of TQM, moderate)
- 63. A production manager at a pottery factory has noticed that about 70 percent of defects result from impurities in raw materials, 15 percent result from human error, 10 percent from machine malfunctions, and 5 percent from a variety of other causes. This manager is most likely using
- 1. a. a Pareto chart
- 2. b. a scatter diagram
- 3. c. a Taguchi loss function
- 4. d. a cause and effect diagram
- 5. e. a flow chart
- a (Tools of TQM, easy)
- 64. A customer service manager at a retail clothing store has collected numerous customer complaints from the forms they fill out on merchandise returns. To analyze trends or patterns in these returns, she has organized these complaints into a small number of categories. This is most closely related to the ____________ tool of TQM.
- 1. a. Taguchi loss function
- 2. b. cause and effect diagram
- 3. c. scatter diagram
- 4. d. histogram
- 5. e. process control chart
- b (Tools of TQM, easy)
- 65. A manager tells her production employees, "It's no longer good enough that your work fall anywhere within the specification limits. I need your work to be as close to the target value as possible." Her thinking is reflective of
- 1. a. internal benchmarking
- 2. b. Six Sigma
- 3. c. ISO 9000
- 4. d. Taguchi concepts
- 5. e. process control charts
- d (Tools of TQM, moderate)
- 66. A fishbone diagram is also known as a
- 1. a. cause-and-effect diagram
- 2. b. poka-yoke diagram
- 3. c. Kaizen diagram
- 4. d. Kanban diagram
- 5. e. Taguchi diagram
- a (Tools of TQM, easy)
- 67. If a sample of parts is measured and the mean of the measurements is outside the control limits, the process is
- 1. a. in control, but not capable of producing within the established control limits
- 2. b. out of control and the process should be investigated for assignable variation
- 3. c. within the established control limits with only natural causes of variation
- 4. d. monitored closely to see if the next sample mean will also fall outside the control limits
- 5. e. none of the above
- b (Tools of TQM, moderate)
- 68. A quality circle holds a brainstorming session and attempts to identify the factors responsible for flaws in a product. Which tool do you suggest they use to organize their findings?
- 1. a. Ishikawa diagram
- 2. b. Pareto chart
- 3. c. process chart
- 4. d. control charts
- 5. e. activity chart
- a (Tools of TQM, moderate) {AACSB: Communication}
- 69. When a sample measurement falls inside the control limits, it means that
- 1. a. each unit manufactured is good enough to sell
- 2. b. the process limits cannot be determined statistically
- 3. c. the process output exceeds the requirements
- 4. d. if there is no other pattern in the samples, the process is in control
- 5. e. the process output does not fulfill the requirements
- d (Tools of TQM, moderate,)
- 70. Which of the following is false regarding control charts?
- 1. a. Values above the upper control limits always imply that the product’s quality is exceeding expectations.
- 2. b. Control charts are built so that new data can be quickly compared to past performance data.
- 3. c. Control charts graphically present data.
- 4. d. Control charts plot data over time.
- 5. e. None of the above is false.
- a (Tools of TQM, moderate)
- 71. The goal of inspection is to
- 1. a. detect a bad process immediately
- 2. b. add value to a product or service
- 3. c. correct deficiencies in products
- 4. d. correct system deficiencies
- 5. e. all of the above
- a (The role of inspection, moderate)
- 72. Which of the following is not a typical inspection point?
- 1. a. upon receipt of goods from your supplier
- 2. b. during the production process
- 3. c. before the product is shipped to the customer
- 4. d. at the supplier's plant while the supplier is producing
- 5. e. after a costly process
- e (The role of inspection, moderate)
- 73. A good description of "source inspection" is inspecting
- 1. a. materials upon delivery by the supplier
- 2. b. the goods at the production facility before they reach the customer
- 3. c. the goods as soon as a problem occurs
- 4. d. goods at the supplier's plant
- 5. e. one's own work, as well as the work done at the previous work station
- e (The role of inspection, moderate)
- 74. "Poka-yoke" is the Japanese term for
- 1. a. card
- 2. b. foolproof
- 3. c. continuous improvement
- 4. d. fishbone diagram
- 5. e. just-in-time production
- b (The role of inspections, moderate) {AACSB: Multiculture and Diversity}
- 75. What refers to training and empowering frontline workers to solve a problem immediately?
- 1. a. just-in-time
- 2. b. poka-yoke
- 3. c. benchmarking
- 4. d. kaizen
- 5. e. service recovery
- e (TQM in services, easy)
- 76. A recent consumer survey conducted for a car dealership indicates that, when buying a car, customers are primarily concerned with the salesperson's ability to explain the car's features, the salesperson's friendliness, and the dealer's honesty. The dealership should be especially concerned with which determinants of service quality?
- 1. a. communication, courtesy, and credibility
- 2. b. competence, courtesy, and security
- 3. c. competence, responsiveness, and reliability
- 4. d. communication, responsiveness, and reliability
- 5. e. understanding/knowing customer, responsiveness, and reliability
- a (TQM in services, moderate) {AACSB: Communication}
- 77. Marketing issues such as advertising, image, and promotion are important to quality because
- 1. a. they define for consumers the tangible elements of a service
- 2. b. the intangible attributes of a product (including any accompanying service) may not be defined by the consumer
- 3. c. they educate consumers on how to use the product
- 4. d. they make the product seem more valuable than it really is
- 5. e. they raise expenses and therefore decrease profitability
- b (TQM in services, moderate)
- 78. Which of the determinants of service quality involves having the customer's best interests at heart?
- 1. a. access
- 2. b. courtesy
- 3. c. credibility
- 4. d. responsiveness
- 5. e. tangibles
- c (TQM in services, moderate)
- 79. Which of the determinants of service quality involves performing the service right the first time?
- 1. a. access
- 2. b. courtesy
- 3. c. credibility
- 4. d. reliability
- 5. e. responsiveness
- d (TQM in services, moderate)
- FILL-IN-THE-BLANK
- 80. Arnold Palmer Hospital uses ___________ to seek new ways to reduce readmission rates.
- continuous improvement (Global company profile, easy)
- 81. ___________ costs result from production of defective parts or services before delivery to the customer.
- Internal failure (Defining quality, moderate)
- 82. _______ is a set of environmental standards developed by the International Standards Organization.
- ISO 14000 (Defining quality, moderate) {AACSB: Ethical Reasoning}
- 83. The work by _________ regarding how people learn from each other’s successes led to the field of cross-functional teamwork.
- Armand Feigenbaum (Defining quality, moderate)
- 84. Not only customers, but stockholders, suppliers, and others, are among the _________ whose values must be protected in making ethical decisions concerning the quality of products.
- stakeholders (Defining quality, easy) {AACSB: Ethical Reasoning}
- 85. _________ is the Japanese word for the ongoing process of incremental improvement.
- Kaizen (Total quality management, moderate) {AACSB: Multiculture and Diversity}
- 86. Enlarging employee jobs so that the added responsibility and authority is moved to the lowest level possible in the organization is called ______________.
- employee empowerment (Total quality management, moderate)
- 87. Respect for _________ is a cornerstone of continuous improvement.
- people (Total quality management, moderate)
- 88. _________ selects a demonstrated standard of performance that represents the very best performance for a process or activity.
- Benchmarking (Total quality management, moderate)
- 89. A group of employees that meet on a regular basis with a facilitator to solve work-related problems in their work area is a(n) _______________.
- quality circle (Total quality management, easy) {AACSB: Communication}
- 90. ___________ diagrams use a schematic technique to discover possible locations of quality problems.
- Cause-and-effect, or fishbone or Ishikawa (Tools of TQM, moderate)
- 91. ________ are graphical presentations of data over time that show upper and lower control limits for processes we want to control.
- Control charts (Tools of TQM, moderate)
- 92. ________ is doing the job properly with the operator ensuring that this is so.
- Source inspection (The role of inspection, moderate)
- SHORT ANSWER
- 93. Identify the four costs of quality. Which one is hardest to evaluate? Explain. The four costs are internal, external, prevention, and appraisal. The hardest to estimate are external costs, or costs that occur after delivery of defective part or services. These costs are very hard to quantify. (Defining quality, moderate)
- 94. State the American Society for Quality’s definition of quality. Of the three "flavors" or categories of quality definitions, which type is it? Explain. Quality is the totality of features and characteristics of a product or service that bear on its ability to satisfy stated or implied needs. This is user-based, as evidenced by the reference to needs, not to specifications or ingredients. (Defining quality, moderate)
- 95. Quality has at least three categories of definitions; identify them. Provide a brief explanation of each. The three categories of quality are user-based (in the eyes of the beholder), manufacturing-based (conforming to standards), and product-based (measurable content of product). (Defining quality, moderate)
- 96. Identify the five steps of DMAIC.
- (1) Define the project’s purpose, scope, and outputs and then identify the required process
- information, keeping in mind the customer’s definition of quality; (2) Measure the process
- and collect data; (3) Analyze the data, ensuring repeatability (the results can be duplicated),
- and reproducibility (others get the same result); (4) Improve, by modifying or redesigning,
- existing processes and procedures; and (5) Control the new process to make sure
- performance levels are maintained.
- (Total quality management, difficult)
- 97. In a sentence or two, summarize the contribution of Philip Crosby to quality management. In his book "Quality Is Free," Crosby pointed out that the costs of poor quality are understated, and that understatement made it easier for firms to accept low quality results. He also promoted "zero defects" and doing the job right the first time. (Defining quality, moderate)
- 98. Identify the five core elements of ISO 14000. The five core elements of ISO 14000 are environmental management, auditing, performance evaluation, labeling, and life cycle assessment. (International quality standards, moderate)
- 99. Describe how ISO 9000 has evolved in the past several years. The standards have become more of a quality management system. These changes came about primarily through the December 2000 revisions. They emphasize top management leadership and customer requirements and satisfaction, while documented procedures now receive less emphasis. (International quality standards, moderate)
- 100. What steps can be taken to develop benchmarks? The steps are: determine what to benchmark, form a benchmarking team, identify benchmarking partners, collect and analyze benchmarking information, and take action to match or exceed the benchmark. (Total quality management, moderate)
- 101. Explain how just-in-time processes relate to the quality of an organization's outputs. JIT relates to quality by cutting costs of quality, by lowering waste and scrap; by improving quality by shortening the time between error detection and error correction; and better quality means less inventory and better JIT system. (Total quality management, moderate)
- 102. What is the difference between conforming quality and target-oriented quality? With conforming quality, any unit that meets specifications is acceptable, whether it is on the edges or center of the specification range. Target-oriented quality treats output as better the closer it is to exactly what the customer wants. (Total quality management, moderate)
- 103. Identify the major concepts of TQM. The major concepts of total quality management are continuous improvement, Six Sigma, employee empowerment, benchmarking, just-in-time (JIT), Taguchi concepts, and knowledge of TQM tools. (Total quality management, moderate)
- 104. What is the quality loss function (QLF)? The quality loss function identifies all costs connected with poor quality and shows how these costs increase as the product moves away from being exactly what the customer wants. (Total quality management, moderate)
- 105. Explain how a Pareto chart can identify the most important causes of errors in a process. There will generally be some causes with much higher frequencies than others. The frequency plot will clearly show which cause has the highest frequency. (Tools of TQM, moderate)
- 106. How is source inspection related to employee empowerment? Source inspection involves the operator ensuring that the job is done properly. These operators are empowered to self-check their own work. Employees that deal with a system on a daily basis have a better understanding of the system than anyone else, and can be very effective at improving the system. (The role of inspection, moderate)
- 107. What is a poka-yoke? Give an example. A poka-yoke is a foolproof device or technique that ensures production of good units every time. Examples will vary, but include McDonald's french fry scoop and standard sized bags used to ensure the correct quantity, and prepackaged surgical coverings that contain exactly the items needed for a medical procedure. (The role of inspection, moderate)
- 108. Identify the ten determinants of service quality. Describe two of them in a sentence or two each. The ten are reliability, responsiveness, competence, access, courtesy, communication, credibility, security, understanding, and tangibles. Descriptions are found in Table 6.5. Here are two examples: Access involves approachability and ease of contact. Security is the freedom from danger, risk, or doubt. (TQM in services, moderate)
- PROBLEMS
- 109. Management is concerned that workers create more product defects at the very beginning and end of a work shift than at other times of their eight hour workday. Construct a scatter diagram with the following data, collected last week. Is management justified in its belief?
- Number of defects
- Monday Tuesday Wednesday Thursday Friday
- First hour at work 12 9 6 8 7
- Second hour at work 6 5 3 4 5
- Third hour at work 5 2 4 3 3
- Fourth hour at work 4 0 5 2 3
- Fifth hour at work 1 6 2 4 5
- Sixth hour at work 4 3 3 2 1
- Seventh hour at work 7 4 4 6 3
- Eighth hour at work 5 7 8 5 9
- Solution:
- There is fairly convincing evidence that there are more defects in the first and last shift hours than at other times. (Tools of TQM, moderate) {AACSB: Analytic Skills}
- 110. Perform a Pareto analysis on the following information:
- Reason for unsatisfying stay at hotel
- Frequency
- 6
- Unfriendly staff
- 2
- Room not clean
- 3
- Room not ready at check-in
- 33
- No towels at pool
- 4
- No blanket for pull-out sofa
- 3
- Pool water too cold
- 16
- Breakfast of poor quality
- 23
- Elevator too slow or not working
- 7
- Took too long to register
- 3
- Bill incorrect
- Total
- 100
- Solution
- (Tools of TQM, moderate) {AACSB: Analytic Skills}
- 111. Perform a Pareto analysis on the following information:
- Reason for unsatisfying check-out at store Frequency
- Unfriendly cashier 27
- Incorrect change 4
- Cashier too slow 9
- Price check 34
- Poorly bagged merchandise 2
- Slow receiving check approval 3
- Solution
- 100
- 80
- 60
- 40
- 20
- 0 100
- 50
- 0
- Price check Cashier too slow Slow receiving check
- Unfriendly cashier Incorrect change Poorly bagged mercha
- (Tools of TQM, moderate) {AACSB: Analytic Skills}
- 112. Construct a cause-and-effect diagram showing why a student might be dissatisfied with the cafeteria.
- Solution: (Note that answers may vary considerably)
- 113. Pretend that you have just come from a relative's wedding reception. It didn't turn out as well as it should have, and the bride's parents are pretty mad at how things turned out. Use the supplied template to construct a conventional cause-and-effect diagram. Identify twelve sources of defects for the issue "dissatisfied customer of wedding reception caterer." (Your dozen need not be exactly three per main cause, but should be a balanced treatment.) Categorize each cause onto a main cause. Provide brief support for each of your choices
- Solution: Individual responses may vary considerably; some of the variation in responses comes from differing views of what is the caterer's realm of responsibility, compared to what might be assigned to a wedding planner instead. Material: not enough plates, glassware, utensils; prepared wrong dish; food was cold; ran out of food; food was "bad." Machinery: air conditioning/heating was broken; room was dirty; room too small; furniture poorly arranged; wedding "props" ugly or shopworn. Method: not on time; overcharged; not enough workers. Manpower: wait staff not properly attired; wait staff not speedy; wait staff not courteous. Responses should comment as necessary to show why a fault lies on a certain main branch; as an example, "cold food" might be interpreted as Method, not Material. (Tools of TQM, moderate) {AACSB: Analytic Skills}
- 114. A refrigeration and heating company—one that installs and repairs home central air and heating systems—has asked your advice on how to analyze their service quality. They have logged customer complaints. Here's a recent sampling. Use the supplied template to construct a conventional cause-and-effect diagram. Place each of the complaints onto a main cause; justify your choice with a brief comment as necessary.
- 1 "I was overcharged—your labor rates are too high."
- 2 "The repairman left trash where he was working."
- 3 "You weren't here when you said you would be. You should call when you must be late."
- 4 "Your repairman smoked in my house."
- 5 "The part you installed is not as good as the factory original."
- 6 "Your repairman was here for over two hours, but he wasn't taking his work seriously."
- 7 "You didn't tighten some of the fittings properly—the system's leaking."
- 8 "Your estimate of repair costs was WAY off."
- 9 "I called you to do an annual inspection, but you've done more—work that I didn't authorize."
- 10 "Your mechanic is just changing parts—he doesn't have a clue what's really wrong."
- 11 "Your bill has only a total—I wanted to see detail billing."
- 12 "Your testing equipment isn't very new—are you sure you've diagnosed the problem?"
- 13 "One of the workmen tracked mud into my living room."
- Solution: Individual responses may vary. A typical set of responses might be Material: item 5. Method: items 1, 3, 8, 9, 11. Machinery: item 12; Manpower: items 2, 4, 6, 7, 10, 13. Items 8 and 11 could be manpower or method. (Tools of TQM, moderate) {AACSB: Analytic Skills}
- SUPPLEMENT 6: STATISTICAL PROCESS CONTROL
- TRUE/FALSE
- 1. Some degree of variability is present in almost all processes.
- True (Statistical Process Control (SPC), easy)
- 2. The purpose of process control is to detect when natural causes of variation are present.
- False (Statistical Process Control (SPC), moderate)
- 3. A normal distribution is generally described by its two parameters: the mean and the range.
- False (Statistical Process Control (SPC), easy)
- 4. A process is said to be in statistical control when assignable causes are the only sources of variation.
- False (Statistical Process Control (SPC), moderate)
- 5. Mistakes stemming from workers' inadequate training represent an assignable cause of variation.
- True (Statistical Process Control (SPC), easy)
- 6. Averages of small samples, not individual measurements, are generally used in statistical process control.
- True (Statistical Process Control (SPC), moderate)
- 7. The X-bar chart indicates that a gain or loss of uniformity has occurred in dispersion of a production process.
- False (Statistical Process Control (SPC), moderate)
- 8. The Central Limit Theorem states that when the sample size increases, the distribution of the sample means will approach the normal distribution.
- True (Statistical Process Control (SPC), moderate)
- 9. In statistical process control, the range often substitutes for the standard deviation.
- True (Statistical Process Control (SPC), moderate)
- 10. If the process average is in control, then the process range must also be in control.
- False (Statistical Process Control (SPC), moderate)
- 11. A process range chart illustrates the amount of variation within the samples.
- True (Statistical Process Control (SPC), moderate)
- 12. Mean charts and range charts complement one another, one detecting shifts in process average, the other detecting shifts in process dispersion.
- True (Statistical Process Control (SPC), moderate)
- 13. X-bar charts are used when we are sampling attributes.
- False (Statistical Process Control (SPC), easy)
- 14. To measure the voltage of batteries, one would sample by attributes.
- False (Statistical Process Control (SPC), easy)
- 15. A p-chart is appropriate to plot the number of typographic errors per page of text.
- False (Statistical Process Control (SPC), easy)
- 16. A c-chart is appropriate to plot the number of flaws in a bolt of fabric.
- True (Statistical Process Control (SPC), easy)
- 17. The x-bar chart, like the c-chart, is based on the exponential distribution.
- False (Statistical Process Control (SPC), moderate)
- 18. A process that is in statistical control will always yield products that meet their design specifications.
- False (Process capability, moderate)
- 19. The higher the process capability ratio, the greater the likelihood that process will be within design specifications.
- True (Process capability, moderate)
- 20. The Cpk index measures the difference between desired and actual dimensions of goods or services produced.
- True (Process capability, moderate)
- 21. Acceptance sampling accepts or rejects an entire lot based on the information contained in the sample.
- True (Acceptance sampling, moderate)
- 22. A lot that is accepted by acceptance sampling is free of defects.
- False (Acceptance sampling, moderate)
- 23. In acceptance sampling, a manager can reach the wrong conclusion if the sample is not representative of the population it was drawn from.
- True (Acceptance sampling, moderate)
- 24. The probability of rejecting a good lot is known as consumer's risk.
- False (Acceptance sampling, moderate)
- 25. An acceptance sampling plan must define "good lots" and "bad lots" and specify the risk level associated with each one.
- True (Acceptance sampling, moderate)
- 26. The acceptable quality level (AQL) is the average level of quality we are willing to accept.
- False (Acceptance sampling, moderate)
- 27. The steeper an OC curve, the better it discriminates between good and bad lots.
- True (Acceptance sampling, moderate)
- MULTIPLE CHOICE
- 28. If a sample of items is taken and the mean of the sample is outside the control limits the process is
- 1. a. out of control and the cause should be established
- 2. b. in control, but not capable of producing within the established control limits
- 3. c. within the established control limits with only natural causes of variation
- 4. d. monitored closely to see if the next sample mean will also fall outside the control limits
- 5. e. producing high quality products
- a (Statistical Process Control (SPC), moderate)
- 29. The causes of variation in statistical process control are
- 1. a. cycles, trends, seasonality, and random variations
- 2. b. producer's causes and consumer's causes
- 3. c. mean and range
- 4. d. natural causes and assignable causes
- 5. e. Type I and Type II
- d (Statistical Process Control (SPC), moderate)
- 30. Natural variations
- 1. a. affect almost every production process
- 2. b. are the many sources of variation that occur when a process is under control
- 3. c. when grouped, form a pattern, or distribution
- 4. d. are tolerated, within limits, when a process is under control
- 5. e. All of the above are true.
- e (Statistical Process Control (SPC), moderate)
- 31. Natural variations
- 1. a. are variations that are to be identified and eliminated
- 2. b. are variations that can be traced to a specific cause
- 3. c. are the same as assignable variations
- 4. d. lead to occasional false findings that processes are out of control
- 5. e. play no role in statistical process control
- d (Statistical Process Control (SPC), moderate)
- 32. Assignable variation
- 1. a. is a sign that a process is under control
- 2. b. is to be identified and eliminated
- 3. c. is the same as random variation
- 4. d. is variation that cannot be traced to a specific cause
- 5. e. leads to a steep OC curve
- b (Statistical Process Control (SPC), moderate)
- 33. Assignable causes
- 1. a. are not as important as natural causes
- 2. b. are within the limits of a control chart
- 3. c. depend on the inspector assigned to the job
- 4. d. are also referred to as "chance" causes
- 5. e. are causes of variation that can be identified and removed
- e (Statistical Process Control (SPC), moderate)
- 34. Control charts for variables are based on data that come from
- 1. a. acceptance sampling
- 2. b. individual items
- 3. c. averages of small samples
- 4. d. averages of large samples
- 5. e. the entire lot
- c (Statistical Process Control (SPC), moderate)
- 35. The purpose of an X chart is to determine whether there has been a
- 1. a. gain or loss in uniformity
- 2. b. change in the percent defective in a sample
- 3. c. change in the central tendency of the process output
- 4. d. change in the number of defects in a sample
- 5. e. change in the AOQ
- c (Statistical Process Control (SPC), moderate)
- 36. Statistical process control charts
- 1. a. display the measurements on every item being produced
- 2. b. display upper and lower limits for process variables or attributes, and signal when a process is no longer in control
- 3. c. indicate to the process operator the average outgoing quality of each lot
- 4. d. indicate to the operator the true quality of material leaving the process
- 5. e. none of the above
- b (Statistical Process Control (SPC), moderate)
- 37. A sample of parts is measured. The mean of this sample is in the middle of the control limits, but some individual parts measure too low for design specifications and other parts measure too high. Which of the following is true?
- 1. a. The process is out of control, and the cause should be established.
- 2. b. The process is in control, but not capable of producing within the established control limits.
- 3. c. The process is within the established control limits with only natural causes of variation.
- 4. d. The process is outside the established control limits with only natural causes of variation.
- 5. e. The process is in control, and there is nothing to worry about.
- b (Statistical Process Control (SPC), difficult)
- 38. The Central Limit Theorem
- 1. a. is the theoretical foundation of the c-chart
- 2. b. states that the average of assignable variations is zero
- 3. c. allows managers to use the normal distribution as the basis for building some control charts
- 4. d. states that the average range can be used as a proxy for the standard deviation
- 5. e. controls the steepness of an operating characteristic curve
- c (Statistical Process Control (SPC), difficult)
- 39. For an x-bar chart where the standard deviation is known, the Upper Control Limit
- 1. a. is 3⋅σ below the mean of sample means for a 3σ control chart
- 2. b. is 3⋅σ above the mean of sample means for a 3σ control chart
- 3. c. is 3⋅σ n below the mean of sample means for a 3σ control chart
- 4. d. is 3⋅σ n above the mean of sample means for a 3σ control chart
- 5. e. cannot be calculated unless the average range is known
- d (Statistical Process Control (SPC), moderate)
- 40. Up to three standard deviations above or below the centerline is the amount of variation that statistical process control allows for
- 1. a. Type I errors
- 2. b. about 95.5% variation
- 3. c. natural variation
- 4. d. all types of variation
- 5. e. assignable variation
- c (Statistical Process Control (SPC), moderate)
- 41. A manager wants to build 3σ control limits for a process. The target value for the mean of the process is 10 units, and the standard deviation of the process is 6. If samples of size 9 are to be taken, the UCL and LCL will be
- 1. a. -8 and 28
- 2. b. 16 and 4
- 3. c. 12 and 8
- 4. d. 4 and 16
- 5. e. 8 and 12
- b (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 42. The type of inspection that classifies items as being either good or defective is
- 1. a. variable inspection
- 2. b. attribute inspection
- 3. c. fixed inspection
- 4. d. all of the above
- 5. e. none of the above
- b (Statistical Process Control (SPC), moderate)
- 43. The x-bar chart tells us whether there has been a
- 1. a. gain or loss in dispersion
- 2. b. change in the percent defective in a sample
- 3. c. change in the central tendency of the process output
- 4. d. change in the number of defects in a sample
- 5. e. none of the above
- c (Statistical Process Control (SPC), moderate)
- 44. The mean and standard deviation for a process for which we have a substantial history are x = 120 and σ = 2. For the variable control chart, a sample size of 16 will be used. What is the mean of the sampling distribution?
- 1. a. 1/8 (0.125)
- 2. b. 0.5
- 3. c. 2
- 4. d. 40
- 5. e. none of the above
- e (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 45. Jars of pickles are sampled and weighed. Sample measures are plotted on control charts. The ideal weight should be precisely 11 oz. Which type of chart(s) would you recommend?
- 1. a. p-charts
- 2. b. c-charts
- 3. c. x-and R-charts
- 4. d. x-, but not R-charts
- 5. e. both p- and c-charts
- c (Statistical Process Control (SPC), moderate)
- 46. If x = 23 ounces, σ = 0.4 ounces, and n = 16, the ±3σ control limits will be
- 1. a. 21.8 to 24.2 ounces
- 2. b. 23 ounces
- 3. c. 22.70 to 23.30 ounces
- 4. d. 22.25 to 23.75 ounces
- 5. e. none of the above
- c (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 47. The usual purpose of an R-chart is to signal whether there has been a
- 1. a. gain or loss in dispersion
- 2. b. change in the percent defective in a sample
- 3. c. change in the central tendency of the process output
- 4. d. change in the number of defects in a sample
- 5. e. none of the above
- a (Statistical Process Control (SPC), moderate)
- 48. A manager wishes to build a 3σ range chart for a process. The sample size is five, the mean of sample means is 16.01, and the average range is 5.3. From Table S6.1, the appropriate value of D3 is 0, and D4 is 2.115. The UCL and LCL for this range chart are
- 1. a. 33.9 and 11.2
- 2. b. 33.9 and 0
- 3. c. 11.2 and 0
- 4. d. 6.3 and 0
- 5. e. 31.91 and 0.11
- c (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 49. Plots of sample ranges indicate that the most recent value is below the lower control limit. What course of action would you recommend?
- 1. a. Since there is no obvious pattern in the measurements, variability is in control.
- 2. b. One value outside the control limits is insufficient to warrant any action.
- 3. c. Lower than expected dispersion is a desirable condition; there is no reason to investigate.
- 4. d. The process is out of control; reject the last units produced.
- 5. e. Variation is not in control; investigate what created this condition.
- e (Statistical Process Control (SPC), difficult)
- 50. To set x-chart upper and lower control limits, one must know the process central line, which is the
- 1. a. average of the sample means
- 2. b. total number of defects in the population
- 3. c. percent defects in the population
- 4. d. size of the population
- 5. e. average range
- a (Statistical Process Control (SPC), moderate)
- 51. According to the text, the most common choice of limits for control charts is usually
- 1. a. ± 1 standard deviation
- 2. b. ± 2 standard deviations
- 3. c. ± 3 standard deviations
- 4. d. ± 3 standard deviations for means and ± 2 standard deviations for ranges
- 5. e. none of the above
- c (Statistical Process Control (SPC), moderate)
- 52. Which of the following is true of a p-chart?
- 1. a. The lower control limit is found by subtracting a fraction from the average number of defects.
- 2. b. The lower control limit indicates the minimum acceptable number of defects.
- 3. c. The lower control limit may be below zero.
- 4. d. The lower control limit may be at zero.
- 5. e. The lower control limit is the same as the lot tolerance percent defective.
- d (Statistical Process Control (SPC), moderate)
- 53. The normal application of a p-chart is in
- 1. a. process sampling by variables
- 2. b. acceptance sampling by variables
- 3. c. process sampling by attributes
- 4. d. acceptance sampling by attributes
- 5. e. none of the above
- c (Statistical Process Control (SPC), moderate)
- 54. The statistical process chart used to control the number of defects per unit of output is the
- 1. a. x-chart
- 2. b. R-chart
- 3. c. p-chart
- 4. d. AOQ chart
- e c-chart
- e (Statistical Process Control (SPC), moderate)
- 55. The c-chart signals whether there has been a
- 1. a. gain or loss in uniformity
- 2. b. change in the number of defects per unit
- 3. c. change in the central tendency of the process output
- 4. d. change in the percent defective in a sample
- 5. e. change in the AOQ
- b (Statistical Process Control (SPC), moderate)
- 56. The local newspaper receives several complaints per day about typographic errors. Over a seven-day period, the publisher has received calls from readers reporting the following number of errors: 4, 3, 2, 6, 7, 3, and 9. Based on these data alone, what type of control chart(s) should the publisher use?
- 1. a. p-chart
- 2. b. c-chart
- 3. c. x-chart
- 4. d. R-chart
- e. x-and R-charts
- b (Statistical Process Control (SPC), moderate)
- 57. A manufacturer uses statistical process control to control the quality of the firm's products. Samples of 50 of Product A are taken, and a defective/acceptable decision is made on each unit sampled. For Product B, the number of flaws per unit is counted. What type(s) of control charts should be used?
- 1. a. p-charts for A and B
- 2. b. p-chart for A, c-chart for B
- 3. c. c-charts for both A and B
- 4. d. p-chart for A, mean and range charts for B
- 5. e. c-chart for A, mean and range charts for B
- b (Statistical Process Control (SPC), difficult)
- 58. A nationwide parcel delivery service keeps track of the number of late deliveries (more than 30 minutes past the time promised to clients) per day. They plan on using a control chart to plot their results. Which type of control chart(s) would you recommend?
- 1. a. x-and R-charts
- 2. b. p-charts
- 3. c. c-charts
- 4. d. x-, but not R-charts
- 5. e. both p- and c-charts
- c (Statistical Process Control (SPC), moderate)
- 59. A run test is used
- 1. a. to examine variability in acceptance sampling plans
- 2. b. in acceptance sampling to establish control
- 3. c. to examine points in a control chart to check for natural variability
- 4. d. to examine points in a control chart to check for nonrandom variability
- 5. e. none of the above
- d (Statistical Process Control (SPC), moderate)
- 60. Which of the following is true regarding the process capability index Cpk?
- 1. a. A Cpk index value of 1 is ideal, meaning all units meet specifications.
- 2. b. The larger the Cpk, the more units meet specifications.
- 3. c. The Cpk index can only be used when the process centerline is also the specification centerline.
- 4. d. Positive values of the Cpk index are good; negative values are bad.
- 5. e. None of the above is true.
- b (Process capability, moderate)
- 61. If the Cpk index exceeds 1
- 1. a. the AQL must be smaller than the LTPD
- 2. b. σ must be less than one-third of the difference between the specification and the process mean
- 3. c. the x-bar chart must indicate that the process is in control
- 4. d. the process is capable of Six Sigma quality
- 5. e. the process is characterized as "not capable"
- b (Process capability, moderate)
- 62. The statistical definition of Six Sigma allows for 3.4 defects per million. This is achieved by a Cpk index of
- 1. a. 0
- 2. b. 1
- 3. c. 1.33
- 4. d. 1.67
- 5. e. 2
- e (Process capability), moderate)
- 63. A Cpk index of 1.00 equates to a defect rate of
- 1. a. five percent
- 2. b. 3.4 defects per million
- 3. c. 2.7 per 1,000 items
- 4. d. 97.23 percent
- 5. e. one percent
- c (Process capability, moderate)
- 64. Acceptance sampling
- 1. a. is the application of statistical techniques to the control of processes
- 2. b. was developed by Walter Shewhart of Bell Laboratories
- 3. c. is used to determine whether to accept or reject a lot of material based on the evaluation of a sample
- 4. d. separates the natural and assignable causes of variation
- 5. e. all of the above
- c (Acceptance sampling, moderate)
- 65. Acceptance sampling's primary purpose is to
- 1. a. estimate process quality
- 2. b. estimate lot quality
- 3. c. detect and eliminate defectives
- 4. d. decide if a lot meets predetermined standards
- 5. e. determine whether defective items found in sampling should be replaced
- d (Acceptance sampling, difficult)
- 66. An acceptance sampling plan's ability to discriminate between low quality lots and high quality lots is described by
- 1. a. a Gantt chart
- 2. b. the Central Limit Theorem
- 3. c. a process control chart
- 4. d. an operating characteristics curve
- 5. e. a range chart
- d (Acceptance sampling, moderate)
- 67. Acceptance sampling
- 1. a. may involve inspectors taking random samples (or batches) of finished products and measuring them against predetermined standards
- 2. b. may involve inspectors taking random samples (or batches) of incoming raw materials and measuring them against predetermined standards
- 3. c. is more economical than 100% inspection
- 4. d. may be either of a variable or attribute type, although attribute inspection is more common in the business environment
- 5. e. All of the above are true.
- e (Acceptance sampling, moderate)
- 68. Which of the following statements on acceptance sampling is true?
- 1. a. Acceptance sampling draws samples from a population of items, tests the sample, and accepts the entire population if the sample is good enough, and rejects it if the sample is poor enough.
- 2. b. The sampling plan contains information about the sample size to be drawn and the critical acceptance or rejection numbers for that sample size.
- 3. c. The steeper an operating characteristic curve, the better its ability to discriminate between good and bad lots.
- 4. d. All of the above are true.
- 5. e. All of the above are false.
- d (Acceptance sampling, moderate)
- 69. Acceptance sampling is usually used to control
- 1. a. the number of units output from one stage of a process which are then sent to the next stage
- 2. b. the number of units delivered to the customer
- 3. c. the quality of work-in-process inventory
- 4. d. incoming lots of purchased products
- 5. e. all of the above
- d (Acceptance sampling, moderate)
- 70. An operating characteristic (OC) curve describes
- 1. a. how many defects per unit are permitted before rejection occurs
- 2. b. the sample size necessary to distinguish between good and bad lots
- 3. c. the most appropriate sampling plan for a given incoming product quality level
- 4. d. how well an acceptance sampling plan discriminates between good and bad lots
- 5. e. none of the above
- d (Acceptance sampling, moderate)
- 71. An operating characteristics curve shows
- 1. a. upper and lower product specifications
- 2. b. product quality under different manufacturing conditions
- 3. c. how the probability of accepting a lot varies with the population percent defective
- 4. d. when product specifications don't match process control limits
- 5. e. how operations affect certain characteristics of a product
- c (Acceptance sampling, moderate)
- 72. Producer's risk is the probability of
- 1. a. accepting a good lot
- 2. b. rejecting a good lot
- 3. c. rejecting a bad lot
- 4. d. accepting a bad lot
- 5. e. none of the above
- b (Acceptance sampling, moderate)
- 73. Which of the following is true regarding the relationship between AOQ and the true population percent defective?
- 1. a. AOQ is greater than the true percent defective.
- 2. b. AOQ is the same as the true percent defective.
- 3. c. AOQ is less than the true percent defective.
- 4. d. There is no relationship between AOQ and the true percent defective.
- 5. e. The relationship between these two cannot be determined.
- c (Acceptance sampling, difficult)
- 74. Average outgoing quality (AOQ) usually
- 1. a. worsens with inspection
- 2. b. stays the same with inspection
- 3. c. improves with inspection
- 4. d. may either improve or worsen with inspection
- 5. e. is the average quality before inspection
- c (Acceptance sampling, moderate)
- 75. A Type I error occurs when
- 1. a. a good lot is rejected
- 2. b. a bad lot is accepted
- 3. c. the number of defectives is very large
- 4. d. the population is worse than the AQL
- 5. e. none of the above
- a (Acceptance sampling, moderate)
- 76. A Type II error occurs when
- 1. a. a good lot is rejected
- 2. b. a bad lot is accepted
- 3. c. the population is worse than the LTPD
- 4. d. the proportion of defectives is very small
- 5. e. none of the above
- b (Acceptance sampling, moderate)
- 77. In most acceptance sampling plans, when a lot is rejected, the entire lot is inspected and all defective items are replaced. When using this technique the AOQ
- 1. a. worsens (AOQ becomes a larger fraction)
- 2. b. improves (AOQ becomes a smaller fraction)
- 3. c. is not affected, but the AQL is improved
- 4. d. is not affected
- 5. e. falls to zero
- b (Acceptance sampling, moderate)
- 78. An acceptance sampling plan is to be designed to meet the organization's targets for product quality and risk levels. Which of the following is true?
- 1. a. n and c determine the AQL.
- 2. b. AQL, LTPD, α and β collectively determine n and c.
- 3. c. n and c are determined from the values of AQL and LTPD.
- 4. d. α and β are determined from the values of AQL and LTPD.
- 5. e. None of the above is true.
- b (Acceptance sampling, moderate)
- 79. A lot that is accepted by acceptance sampling
- 1. a. has more defects than existed before the sampling
- 2. b. has had all its defects removed by 100% inspection
- 3. c. will have the same defect percentage as the LTPD
- 4. d. has no defects present
- 5. e. All of the above are false.
- e (Acceptance sampling, moderate)
- 80. Which of the following statements about acceptance sampling is true?
- 1. a. The steeper an OC curve, the better it discriminates between good and bad lots.
- 2. b. Acceptance sampling removes all defective items.
- 3. c. Acceptance sampling of incoming lots is replacing statistical process control at the supplier.
- 4. d. Acceptance sampling occurs continuously along the assembly line.
- 5. e. All of the above are true.
- a (Acceptance sampling, moderate)
- 81. Which of the following is true regarding the average outgoing quality level?
- 1. a. An AOQ value of 1 is ideal, because all defects have been removed.
- 2. b. AOQ is always greater than AQL but less than LTPD.
- 3. c. AOQ rises (worsens) following inspection of failed lots.
- 4. d. AOQ is very low (very good) for extremely poor quality lots.
- 5. e. None of the above is true.
- d (Acceptance sampling, difficult)
- FILL-IN-THE-BLANK
- 82. _____________ is variation in a production process that can be traced to specific causes.
- Assignable variation (Statistical Process Control (SPC), moderate)
- 83. The _________ is the chief way to control attributes.
- P-chart (Statistical Process Control (SPC), moderate)
- 84. If a process has only natural variations, _________ percent of the time the sample averages will fall inside the ± 3σ n (or ± 3σ x ) control limits.
- 99.73 (Statistical Process Control (SPC), easy)
- 85. The _________ is a quality control chart that indicates when changes occur in the central tendency of a production process. x-bar chart (Statistical Process Control (SPC), moderate)
- 86. The _________ are calculated to show how much allowance should be made for natural variation.
- UCL and LCL, or upper and lower control limits (Statistical Process Control (SPC), easy)
- 87. The _________ is a quality control chart used to control the number of defects per unit of output.
- c-chart (Statistical Process Control (SPC), moderate)
- 88. The term _________ is used to describe how well a process makes units within design specifications (or tolerances). process capability (Process capability, moderate)
- 89. A Cpk index greater than _________ is a capable process, one that generates fewer than 2.7 defects per 1000 at the ± 3σ level. unity, or 1 (Process capability, moderate)
- 90. ___________ is a method of measuring samples of lots or batches of product against predetermined standards. Acceptance sampling (Acceptance sampling, moderate)
- 91. A(n) _____________ is a graph that describes how well an acceptance plan discriminates between good and bad lots. OC or operating characteristics curve (Acceptance sampling, moderate)
- 92. The __________ is the poorest level of quality that we are willing to accept.
- AQL or acceptable quality level (Acceptance sampling, moderate)
- 93. The ____________ is the percent defective in an average lot of goods inspected through acceptance sampling. AOQ or average outgoing quality (Acceptance sampling, moderate)
- SHORT ANSWER
- 94. What is the basic objective of a process control system? It is to provide a statistical signal when assignable causes of variation are present. (Statistical Process Control (SPC), moderate)
- 95. Briefly explain what the Central Limit Theorem has to do with control charts. The CLT underlies the distribution of sample means and the standard deviation of sample means. It leads to the usability of the normal distribution in control charts. (Statistical Process Control (SPC), moderate)
- 96. What are the three possible results (or findings) from the use of control charts? The results of a control chart can indicate (a) in control and capable, (b) in control but not capable, and (c) out of control. (Statistical Process Control (SPC), moderate)
- 97. Why do range charts exist? Aren't x-bar charts enough? Range charts and mean charts perform different functions. The mean chart is used to detect changes in the average of a process. But that average might stay the same while output is getting more scattered. The purpose of the range chart is to detect changes in the dispersion of a process. (Statistical Process Control (SPC), moderate)
- 98. Examine the Statistical Process Control outputs below. Answer the following questions.
- 1. a. What is the sample size?
- 2. b. What is the number of samples?
- 3. c. What is the mean of sample 8; what is the range of sample 10?
- d.. Is this process in control? Explain--a simple Yes or No is insufficient.
- 4. e. What additional steps should the quality assurance team take?
- The sample size is 4; ten samples were taken. The mean of sample 8 is 12.175; the range of sample 10 is 0.5. This chart is built on 2-sigma limits, so the probability of a false signal is about 4.5%. The process is not in control—while all means are within limits, the range for sample 3 is too large. Investigate for assignable cause and eliminate that cause. (Statistical Process Control (SPC), difficult) {AACSB: Analytic Skills}
- 99. Can "in control" and "capable" be shown on the same chart? Only indirectly. The chart illustrating control plots the averages of small samples, while "Capability" is based on the dimensions of individual units. Figure S6.2 suggests that an overly wide range for sample means implies an overly large range for individual values as well. (Statistical Process Control (SPC), moderate)
- 100. What is the difference between natural and assignable causes of variation? Natural variations are those variations that are inherent in the process and for which there is no identifiable cause. These variations fall in a natural pattern. Assignable causes are variations beyond those that can be expected to occur because of natural variation. Thesevariations can be traced to a specific cause. (Statistical Process Control (SPC), moderate)
- 101. Why are X and R-charts usually used hand in hand? The ultimate goal of the X and R-charts is to ascertain, by a sampling procedure, that the relevant parameter is kept within specific upper and lower bounds. The X-bar chart alone tells us only that the average or variable values are within the appropriate limits. The combination of X and the R-charts allows one to determine that both the average and the deviations are within the limits. (Statistical Process Control (SPC), moderate)
- 102. What does it mean for a process to be "capable"? Process capability implies that the natural variation of the process must be small enough to produce products that meet the specifications or tolerances required. (Process capability, moderate)
- 103. What is the difference between the process capability ratio Cp and the process capability index Cpk? The Cp ratio does not consider how well the process average is centered on the target value. However, Cpk does consider how well the process is centered. (Process capability, moderate)
- 104. A process is operating in such a manner that the mean of the process is exactly on the lower specification limit. What must be true about the two measures of capability for this process? The Cp ratio does not consider how well the process average is centered on the target value; its value is unaffected by the setting for the process mean. However, Cpk does consider how well the process is centered; with x-bar on the LSL, the formula guarantees a Cpk of zero. (Process capability, moderate)
- 105. What is acceptance sampling? Acceptance sampling is a method of measuring random samples of lots or batches of products against predetermined standards. (Acceptance sampling, moderate)
- 106. Why doesn't acceptance sampling remove all defects from a batch? Acceptance sampling is a method of measuring random samples of lots or batches of products against predetermined standards. Acceptance sampling is not 100 percent inspection. Based on sampling results, the entire batch is either accepted or rejected. A batch may contain small numbers of defects and still meet the standard for acceptance. (Acceptance sampling, moderate)
- 107. What is the purpose of the Operating Characteristics curve? An OC curve plots the probability of acceptance against the percentage of defects in the lot. It therefore shows how well an acceptance sampling plan discriminates between good and bad lots. (Acceptance sampling, moderate)
- 108. What is the AOQ of an acceptance sampling plan? The AOQ is the average outgoing quality. It is the percent defective in an average lot of goods inspected through an acceptance sampling plan. (Acceptance sampling, moderate)
- 109. Define consumer's risk. How does it relate to the errors of hypothesis testing? What is the symbol for its value? The consumer's risk is the probability of accepting a bad lot. It is a Type II error; its value is beta. (Acceptance sampling, moderate)
- 110. What four elements determine the value of average outgoing quality? Why does this curve rise, peak, and fall? The four elements are the true percent defective of the lot, the probability of accepting the lot, the number of items in the lot, and the number of items in the sample. AOQ is near zero for very good output (which has few defects to find) and for very bad output (which often fails inspection and has its defects removed). AOQ has higher values for output of intermediate quality, for which the probability of rejection is not very high. (Acceptance sampling, moderate)
- 111. What do the terms producer's risk and consumer's risk mean? Producer’s risk: the risk of rejecting a good lot; Consumer’s risk: the risk of accepting a defective lot (Acceptance sampling, moderate)
- 112. Pierre's Motorized Pirogues and Mudboats is setting up an acceptance sampling plan for the special air cleaners he manufactures for his boats. His specifications, and the resulting plan, are shown on the POM for Windows output below. In relatively plain English (someone else will translate for Pierre), explain exactly what he will do when performing the acceptance sampling procedure, and
- Pierre should select samples of size 175 from his lots of air cleaners. He should count the number of defects in each sample. If there are 4 or fewer defects, the lot passes inspection. If there are 5 or more defects, the lot fails inspection. Lots that fail can be handled several ways: they can be 100% inspected to remove defects; they can be sold at a discount; they can be destroyed; they can be sent back for rework, etc. (Acceptance sampling, moderate) {AACSB: Analytic Skills}
- 113. Pierre's Motorized Pirogues and Mudboats is setting up an acceptance sampling plan for the special air cleaners he manufactures for his boats. His specifications, and the resulting plan, are shown on the POM for Windows output below. Pierre is a bit confused. He mistakenly thinks that acceptance sampling will reject all bad lots and accept all good lots. Explain why this will not happen.
- Acceptance sampling cannot discriminate perfectly between good and bad lots; this is illustrated by the OC curve that is not straight up and down. In this example, "good" lots will still be rejected almost 5% of the time. "Bad" lots will still be accepted almost 5% of the time. (Acceptance sampling, moderate)
- 114. Pierre's Motorized Pirogues and Mudboats is setting up an acceptance sampling plan for the special air cleaners he manufactures for his boats. His specifications, and the resulting plan, are shown on the POM for Windows output below. Pierre wants acceptance sampling to remove ALL defects from his production of air cleaners. Explain carefully why this won't happen.
- Acceptance sampling is not intended to remove all defects, nor will it. Consider a lot with a defect rate of 0.005 in this example. If the sample is representative, the lot will pass inspection--which means that no one will inspect the lot for defects. The defects that were present before sampling are still there. Generally, acceptance sampling passes some lots and rejects others. Defects can only be removed from those lots that fail inspection. (Acceptance sampling, moderate)
- PROBLEMS
- 115. A quality analyst wants to construct a sample mean chart for controlling a packaging process. He knows from past experience that the process standard deviation is two ounces. Each day last week, he randomly selected four packages and weighed each. The data from that activity appears below.
- Day Package 1 Weight Package 2 Package 3 Package 4
- Monday Tuesday Wednesday Thursday Friday 23 23 20 18 18 22 2321 1919 2019 2020 22 24 21 21 19 20
- 1. (a) Calculate all sample means and the mean of all sample means.
- 2. (b) Calculate upper and lower control limits that allow ± 2σ for natural variations.
- 3. (c) Is this process in control?
- 1. (a) The five sample means are 23, 21, 20, 19, and 20. The mean of all sample means is 20.6
- 2. (b) UCL = 20.6 + 2 ⋅ 2 4 = 22.6; LCL = 20.6 −2 ⋅ 2 4 = 18.6
- 3. (c) Sample 1 is above the UCL; all others are within limits. The process is out of control. (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 116. A quality analyst wants to construct a sample mean chart for controlling a packaging process. He knows from past experience that when the process is operating as intended, packaging weight is normally distributed with a mean of twenty ounces, and a process standard deviation of two ounces. Each day last week, he randomly selected four packages and weighed each. The data from that activity appears below.
- Day Package 1 Weight Package 2 Package 3 Package 4
- Monday Tuesday Wednesday Thursday Friday 23 23 20 18 18 22 2321 1919 2019 2020 22 24 21 21 19 20
- 1. (a) If he sets an upper control limit of 21 and a lower control limit of 19 around the target value of twenty ounces, what is the probability of concluding that this process is out of control when it is actually in control?
- 2. (b) With the UCL and LCL of part a, what do you conclude about this process—is it in control?
- 3. (a) These control limits are one standard error away from the centerline, and thus include
- 68.268 percent of the area under the normal distribution. There is therefore a 31.732 percent chance that, when the process is operating in control, a sample will indicate otherwise.
- (b) The mean of sample 1 lies outside the control limits. All other points are on or within the
- limits. The process is not in control. (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 117. An operator trainee is attempting to monitor a filling process that has an overall average of 705 cc. The average range is 17 cc. If you use a sample size of 6, what are the upper and lower control limits for the X-bar and R chart?
- From table, A2 = 0.483, D4 = 2.004, D3 = 0
- 118. UCL x = x + A2 * R LCL x = x - A2 * R UCLR = D4 * R LCLR = D3 * R = 705 + 0.483 x 17 = 705 - 0.483 * 17 = 2.004 * 17 = 0 * 17 = 713.211 = 696.789 = 34.068 = 0 (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills} The defect rate for a product has historically been about 1.6%. What are the upper and lower control chart limits for a p-chart, if you wish to use a sample size of 100 and 3-sigma limits?
- UCLp = p + 3 p(1− p) = 0.016 + 3 . (0.016 * 0.984) /100 = .0536
- n
- LCLp = p − 3 p(1− p) = 0.016 - 3 . (0.016 * 0.984) /100 = -0.0216, or zero.
- n
- (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 119. A small, independent amusement park collects data on the number of cars with out-of-state license plates. The sample size is fixed at n=25 each day. Data from the previous 10 days indicate the following number of out-of-state license plates:
- Out-of-state
- Day Plates
- 1 6
- 2 4
- 3 5
- 4 7
- 5 8
- 6 3
- 7 4
- 8 5
- 9 3
- 10 11
- (a) Calculate the overall proportion of "tourists" (cars with out-of-state plates) and the standard deviation of proportions.
- (b) Using ± 3σ limits, calculate the LCL and UCL for these data.
- (c) Is the process under control? Explain.
- (a) p-bar is 56/250 = 0.224; the standard deviation of proportions is the square root of .224 x .776 / 25 = 0.0834
- (b) UCL = .224 + 3 x 0.834 = .4742; LCL = .224 -3 x .0834 which is negative, so the LCL = 0
- (c) The largest percentage of tourists (day 10) is 11/25 = .44, which is still below the UCL. Thus, all the points are within the control limits, so the process is under control. (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 120. Cartons of Plaster of Paris are supposed to weigh exactly 32 oz. Inspectors want to develop process control charts. They take ten samples of six boxes each and weigh them. Based on the following data, compute the lower and upper control limits and determine whether the process is in control.
- Sample Mean Range
- 1 33.8 1.1
- 2 34.6 0.3
- 3 34.7 0.4
- 4 34.1 0.7
- 5 34.2 0.3
- 6 34.3 0.4
- 7 33.9 0.5
- 8 34.1 0.8
- 9 34.2 0.4
- 10 34.4 0.3
- n = 6; overall mean = 34.23; R = 0.52.
- Upper control limit 34.48116 1.04208
- Center line 34.23 0.52
- Lower control limit 33.97884 0
- 1 2 3 4 5 6 7 8 910
- Sample
- The mean values for samples 1, 2, 3, and 7 fall outside the control limits on the X-bar chart and sample 1 falls outside the upper limit on the R-chart. Therefore, the process is out of control. (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 121. McDaniel Shipyards wants to develop control charts to assess the quality of its steel plate. They take ten sheets of 1" steel plate and compute the number of cosmetic flaws on each roll. Each sheet is 20' by 100'. Based on the following data, develop limits for the control chart, plot the control chart, and determine whether the process is in control.
- Number of
- Sheet flaws
- 1 1
- 2 1
- 3 2
- 4 0
- 5 1
- 6 5
- 7 0
- 8 2
- 9 0
- 10 2
- Total units sampled 10
- Total defects 14
- Defect rate, c-bar 1.4
- Standard deviation 1.183216
- z value 3
- Upper Control Limit 4.949648
- Center Line 1.4
- Lower Control Limit 0
- Sample six is above the control limits; therefore, the process is out of control. (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 122. The mean and standard deviations for a process are x = 90 and σ = 9. For the variable control chart, a sample size of 16 will be used. Calculate the standard deviation of the sampling distribution. Sigma x-bar = 9 / 16 = 2.25
- (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 123. If x = 9 ounces, σ = 0.5 ounces, and n = 9, calculate the 3-sigma control limits.
- 8.50 to 9.50 ounces
- (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 124. A hospital-billing auditor has been inspecting patient bills. While almost all bills contain some errors, the auditor is looking now for large errors (errors in excess of $250). Among the last 100 bills inspected, the defect rate has been 16%. Calculate the upper and lower limits for the billing process for 99.7% confidence.
- 0.16 plus or minus 3 x 0.03667, or .050 to 0.270
- (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 125. A local manufacturer supplies you with parts, and you would like to install a quality monitoring system at his factory for these parts. Historically, the defect rate for these parts has been 1.25 percent (You've observed this from your acceptance sampling procedures, which you would like to discontinue). Develop ± 3σ control limits for this process. Assume the sample size will be 200 items.
- p-bar is 0.0125; the standard error of the proportion is
- The upper control limit is 0.0125 + 3 x 0.00786 = 0.03608; the lower control limit is
- 0.0125 – 3 x 0.00786 which is negative, so the LCL is 0.
- (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 126. Repeated sampling of a certain process shows the average of all sample ranges to be 1.0 cm. The sample size has been constant at n = 5. What are the 3-sigma control limits for this R-chart?
- zero to 2.115
- (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 127. A woodworker is concerned about the quality of the finished appearance of her work. In sampling units of a split-willow hand-woven basket, she has found the following number of finish defects in ten units sampled: 4, 0, 3, 1, 2, 0, 1, 2, 0, 2.
- 1. a. Calculate the average number of defects per basket
- 2. b. If 3-sigma control limits are used, calculate the lower control limit, centerline, and upper control limit.
- (a) 1.5; (b) 0, 1.5, and 5.2.
- (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 128. The width of a bronze bar is intended to be one-eighth of an inch (0.125 inches). Inspection samples contain five bars each. The average range of these samples is 0.01 inches. What are the upper and lower control limits for the X-bar and R-chart for this process, using 3-sigma limits?
- X-bar: LCL = .119; UCL =.131. R: LCL = 0.0; UCL =.021
- (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 129. A part that connects two levels should have a distance between the two holes of 4". It has been determined that X-bar and R-charts should be set up to determine if the process is in statistical control. The following ten samples of size four were collected. Calculate the control limits, plot the control charts, and determine if the process is in control.
- Mean Range
- Sample 1
- 4.01 0.04
- Sample 2
- 1 0.06
- Sample 3
- 2 0.02
- Sample 4
- 1 0.05
- Sample 5
- 2 0.06
- Sample 6
- 1 0.02
- Sample 7
- 2 0.02
- Sample 8
- 3.99 0.04
- Sample 9
- 3.98 0.05
- Sample 10
- 4.01 0.06
- X-bar Range x-bar value 3.998 R bar 0.042 Upper control limit 4.029 0.096 Center line 3.998 0.042 Lower control limit 3.967 0
- The process is out of control because of sample 5 on the X-bar chart. (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 130. Ten samples of size four were taken from a process, and their weights measured. The sample averages and sample ranges are in the following table. Construct and plot an X-bar and R-chart using this data. Is the process in control?
- Sample Mean Range
- a. 1 20.01 0.45
- b. 2 19.98 0.67
- c. 3 20.25 0.30
- d. 4 19.90 0.30
- e. 5 20.35 0.36
- f. 6 19.23 0.49
- g. 7 20.01 0.53
- h. 8 19.98 0.40
- i. 9 20.56 0.95
- 10 19.97 0.79
- X-bar Range x-bar value 20.024
- R bar 0.524
- Upper control limit 20.406 1.196 Center line 20.024 0.524 Lower control limit 19.642 0
- The X-bar chart is out of control, and therefore the process is out of control, because samples 6 and 9 are outside of the control limits. (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 131. Larry's boat shop wants to monitor the number of blemishes in the paint of each boat. Construct a c-chart to determine if their paint process is in control using the following data.
- Sample Number Number of
- Defects
- 1 3
- 2 4
- 3 2
- 4 1
- 5 3
- 6 2
- 7 1
- 8 4
- 9 2
- 10 3
- Total units sampled 10
- Total defects 25
- Defect rate, c-bar 2.5
- Standard deviation 1.581
- z value 3
- Upper Control Limit 7.243
- Center Line 2.5
- Lower Control Limit 0
- The process is in control. (Statistical Process Control (SPC), moderate) {AACSB: Analytic Skills}
- 132. The specifications for a manifold gasket that installs between two engine parts calls for a thickness of 2.500 mm + .020 mm. The standard deviation of the process is estimated to be 0.004 mm. What are the upper and lower specification limits for this product? The process is currently operating at a mean thickness of 2.50 mm. (a) What is the Cp for this process? (b) About what percent of all units of this liner will meet specifications? Does this meet the technical definition of Six Sigma?
- (a) LSL = 2.48 mm, USL = 2.52 mm. Cp = (2.52 – 2.48)/(6*0.004) = 1.67. (b) Each specification limit lies 5 standard deviations from the centerline, so practically 100 percent of units will meet specifications. However, this percentage is not quite as high as Six Sigma would call for. (Process capability, moderate) {AACSB: Analytic Skills}
- 133. The specifications for a manifold gasket that installs between two engine parts calls for a thickness of 2.500 mm + .020 mm. The standard deviation of the process is estimated to be 0.004 mm. What are the upper and lower specification limits for this product? The process is currently operating at a mean thickness of 2.50 mm. (a) What is the Cp for this process? (b) The purchaser of these parts requires a capability index of 1.50. Is this process capable? Is this process good enough for the supplier? (c) If the process mean were to drift from its setting of 2.500 mm to a new mean of 2.497, would the process still be good enough for the supplier's needs?
- (a) LSL = 2.48 mm, USL = 2.52 mm. Cp = (2.52 – 2.48)/(6*0.004) = 1.67. (b) Yes to both parts of the question. (c) The Cpk index is now relevant, and its value is the lesser of 1.917 and 1.417. The process is still capable, but not to the supplier's needs. (Process capability, moderate) {AACSB: Analytic Skills}
- 134. The specification for a plastic liner for concrete highway projects calls for a thickness of 6.0 mm ±
- 0.1 mm. The standard deviation of the process is estimated to be 0.02 mm. What are the upper and lower specification limits for this product? The process is known to operate at a mean thickness of
- 6.03 mm. What is the Cp and Cpk for this process? About what percent of all units of this liner will meet specifications? LSL = 5.9 mm, USL = 6.1 mm. Cp is (6.1-5.9)/6(.02) = 1.67. Cpk is the lesser of (6.1¬6.03)/(3*0.02) = 1.17 and (5.9 - 6.03)/(3*0.02) = 2.17; therefore, 1.17. The upper specification limit lies about 3 standard deviations from the centerline, and the lower specification limit is further away, so practically all units will meet specifications. (Process capability, moderate) {AACSB: Analytic Skills}
- 135. The specification for a plastic handle calls for a length of 6.0 inches ± .2 inches. The standard deviation of the process is estimated to be 0.05 inches. What are the upper and lower specification limits for this product? The process is known to operate at a mean thickness of 6.1 inches. What is the Cp and Cpk for this process? Is this process capable of producing the desired part? LSL = 5.8 inches, USL = 6.2 inches. Cp is (6.2-5.8)/6(.05) = 1.33. Cpk is the lesser of (6.2¬6.1)/(3*0.05) = .67 and (5.8 - 6.1)/(3*0.02) = 2.00; therefore, .67. The process is capable based upon the Cp. However, the process is not centered (based upon its Cpk) and based upon its current center is not producing parts that are of an acceptable quality. (Process capability, moderate) {AACSB: Analytic Skills}
- 136. In the table below are selected values for the OC curve for the acceptance sampling plan n=210, c=6. Upon failed inspection, defective items are replaced. Calculate the AOQ for each data point. (You may assume that the population is much larger than the sample.) Plot the AOQ curve. At approximately what population defective rate is the AOQ at its worst? Explain how this happens. How well does this plan meet the specifications of AQL=0.015, α =0.05; LTPD=0.05, β =0.10? Discuss.
- Population percent defective Probability of acceptance
- 0.00 1.00000
- 0.01 0.99408
- 0.02 0.86650
- 0.03 0.55623
- 0.04 0.26516
- 0.05 0.10056
- 0.06 0.03217
- 0.07 0.00905
- 0.08 0.00231
- 0.09 0.00054
- 0.10 0.00012
- The plan meets the α and the β specification fairly well.
- Population percent defective Probability of acceptance AOQ
- 0.00 1.000 0.0000
- 0.01 0.994 0.0099
- 0.015 0.958 0.0144 At AQL
- 0.02 0.867 0.0173 maximum
- 0.03 0.558 0.0167
- 0.04 0.267 0.0107
- 0.05 0.102 0.0051 At LTPD
- 0.06 0.033 0.0020
- 0.07 0.009 0.0006
- 0.08 0.002 0.0002
- 0.09 0.001 0.0001
- (Acceptance sampling, moderate) {AACSB: Analytic Skills}
- 137. In the table below are selected values for the OC curve associated with the acceptance sampling plan n=50, c=1. (Watch out--the points are not evenly spaced.) Assume that upon failed inspection, defective items are replaced. Calculate the AOQ for each data point. (You may assume that the population is much larger than the sample.) Plot the AOQ curve. At approximately what population defective rate is the AOQ at its worst? Explain how this happens. How well does this plan meet the specifications of AQL=0.0050, α =0.05; LTPD=0.05, •β =0.10? Discuss.
- Population percent defective Probability of acceptance
- 0.005 0.97387
- 0.01 0.91056
- 0.02 0.73577
- 0.03 0.55528
- 0.04 0.40048
- 0.05 0.27943
- 0.06 0.19000
- 0.08 0.08271
- This plan does not meet the specification very well. At .005 defective, the probability of
- Population percent defective Probability of acceptance AOQ
- 0.005 0.97387 0.004869 at AQL
- 0.01 0.91056 0.009106
- 0.02 0.73577 0.014715
- 0.03 0.55528 0.016658 maximum
- 0.04 0.40048 0.016019
- 0.05 0.27943 0.013972 at LTPD
- 0.06 0.19000 0.0114
- 0.08 0.08271 0.006617
- (Acceptance sampling, moderate) {AACSB: Analytic Skills}
- 138. A bank’s manager has videotaped 20 different teller transactions to observe the number of mistakes being made. Ten transactions had no mistakes, five had one mistake and five had two mistakes. Compute proper control limits at the 90% confidence level.
- A c-chart should be used, and from Table S6.2, the z-value = 1.65.
- The mean c-bar = [10(0) + 5(1) + 5(2)]/20 = 0.75.
- UCLc = 0.75 +1.65 0.75 = 2.18.
- LCLc = 0.75 −1.65 0.75 =−0.68 (or 0).
- (Statistical process control (SPC), moderate) {AACSB: Analytic Skills}
- 139. A department chair wants to monitor the percentage of failing students in classes in her department. Each class had an enrollment of 50 students last spring. The number of failing students in the 10 classes offered that term were 1, 4, 2, 0, 0, 0, 0, 0, 0, and 3, respectively. Compute the control limits for a p-chart at the 95% confidence level. Is the process in control?
- From Table S6.2, the z-value = 1.96.
- The mean p-bar = [1+4+2+0+0+0+0+0+0+3]/(50×10) = 0.02.
- UCLp = 0.02 + 1.96(.0198) = 0.0589.
- LCLp = 0.02 − 1.96(.0198) = −0.0189 (or 0).
- Since the percent defects in classes 2 and 10 both exceeded 5.89%, the percentage of failing
- students is not in statistical control. The department chair should investigate.
- (Statistical process control (SPC), moderate) {AACSB: Analytic Skills}