Ch17 Maintenance & Reliability – Test Bank | 10e

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Operations Management, 10e, Global Edition (Heizer/Render)

Chapter 17 Maintenance and Reliability

1) Orlando Utilities Commission uses a computerized maintenance management program, and devotes significant dollar and labor resources to power plant maintenance, because the costs of unexpected failure are incredibly high.

Diff: 1

Topic: Global company profile

AACSB: Use of IT

Objective: no LO

2) Maintenance includes all activities involved in keeping a system's equipment in working order.

Diff: 1

Topic: The strategic importance of maintenance and reliability

Objective: no LO

3) Reliability is the probability that a machine part or product will function properly for a specified time regardless of conditions.

Diff: 1

Topic: The strategic importance of maintenance and reliability

Objective: no LO

4) The product failure rate is the percentage of failures among the total number of products tested.

Diff: 2

Topic: Reliability

Objective: no LO

5) The MTBF (mean time between failures) is calculated as the reciprocal of the number of failures during a period of time.

Diff: 2

Topic: Reliability

Objective: LO17-3

6) If the mean time between failures has been calculated to be 2,000 hours, then the number of unit failures per 2,000 hours must be one.

Diff: 2

Topic: Reliability

Objective: LO17-3

7) The reliability of a system in which each individual component must function in order for the entire system to function, and in which each component has its own unique reliability, independent of other components, is the product of the probabilities of each of those components.

Diff: 2

Topic: Reliability

Objective: LO17-2

8) Adding an additional part to a component or product ordinarily reduces reliability by introducing an additional source of failure.

Diff: 2

Topic: Reliability

Objective: LO17-2

9) A redundant part or component increases reliability because it is connected in parallel, not in series.

Diff: 2

Topic: Reliability

Objective: LO17-2

10) A redundant part decreases reliability if the reliability of the redundant part is lower than that of the part it is backing up.

Diff: 2

Topic: Reliability

Objective: LO17-2

11) Preventive maintenance is reactive.

Diff: 2

Topic: Maintenance

Objective: LO17-4

12) Preventive maintenance is nothing more than keeping the equipment and machinery running.

Diff: 2

Topic: Maintenance

Objective: LO17-4

13) Preventive maintenance implies that we can determine when a system needs service or will need repair.

Diff: 2

Topic: Maintenance

Objective: LO17-4

14) Infant mortality refers to the high failure rate often encountered in the very early stages of the lifetime of a product.

Diff: 2

Topic: Maintenance

Objective: LO17-4

15) The failure distributions of products, machines, or processes that have "settled in," or gone beyond the infant mortality phase, often follow the normal distribution.

Diff: 1

Topic: Maintenance

Objective: LO17-4

16) Recording the maintenance history of processes, machines, or equipment is important for preventive maintenance, but largely irrelevant for breakdown maintenance.

Diff: 1

Topic: Maintenance

Objective: LO17-4

17) The "full cost view of maintenance" results in more firms choosing a policy of breakdown maintenance, when compared to the "traditional view of maintenance."

Diff: 1

Topic: Maintenance

Objective: LO17-4

18) Failures are tolerable as long as their results are not catastrophic.

Diff: 2

Topic: Maintenance

Objective: LO17-4

19) Small standard deviations in the MTBF distribution of a machine tend to support a policy of breakdown maintenance for that machine.

Diff: 2

Topic: Maintenance

Objective: LO17-4

20) When identifying the optimal maintenance policy, the cost of inventory maintained to compensate for the downtime is a cost often ignored.

Diff: 2

Topic: Maintenance

Objective: LO17-4

21) An optimal maintenance policy strikes a balance between the costs of breakdown and preventive maintenance so that the total cost of maintenance is at a minimum.

Diff: 2

Topic: Maintenance

Objective: LO17-4

22) While breakdowns occur randomly, their frequency is somewhat predictable through such tools as the product failure rate, MTBF, and the breakdown costs model.

Diff: 2

Topic: Maintenance

Objective: LO17-4

23) The objective of maintenance and reliability is to maintain the capability of the system.

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: no LO

24) TPM (total productive maintenance) is an application of TQM (total quality management) principles to the area of maintenance.

Diff: 2

Topic: Total productive maintenance

Objective: no LO

25) Simulation models and expert systems are useful tools for determining maintenance policies.

Diff: 2

Topic: Techniques for enhancing maintenance

AACSB: Use of IT

Objective: no LO

26) Which of the following statements about maintenance at Orlando Utilities Commission is false?

A) There are at least two types of preventive maintenance, including an annual maintenance and a less frequent overhaul schedule.

B) Its preventive maintenance program has earned the company top rankings and its competitive advantage.

C) Each power-generating unit is taken off-line every three years for a complete overhaul.

D) Each of its power-generating units is taken off-line for maintenance every one to three weeks.

E) Costs associated with breakdowns are several times higher than costs arising from preventive maintenance.

Diff: 2

Topic: Global company profile

Objective: no LO

27) The objective of maintenance and reliability is to

A) ensure that breakdowns do not affect the quality of the products

B) ensure that no breakdowns will ever occur

C) ensure that preventive maintenance costs are kept as low as possible

D) maintain the capability of the system

E) ensure that maintenance employees are fully utilized

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: no LO

28) The probability that a product will function properly for a specified time under stated conditions is

A) functionality

B) maintenance

C) durability

D) reliability

E) fitness for use

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: no LO

29) Which of the following best illustrates the importance of employee involvement in achieving successful maintenance and reliability?

A) Operator, machine, and mechanic are independent of one another.

B) Small standard deviations tend to favor preventive maintenance over breakdown maintenance.

C) Infant mortality in products can be decreased through improved owner's manuals and after-sales service and customer training.

D) Employee involvement through such elements as reward systems and power sharing combine with good maintenance and reliability procedures to improve capacity and reduce variability.

E) Empowered operators have higher competence at repairs than field service or depot service.

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: no LO

30) Which of the following is a maintenance tactic?

A) implementing or improving preventative checks

B) increasing repair speed

C) providing redundancy

D) A and B

E) A, B, and C

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: LO17-5

31) What is the reliability of a four-component product, with components in series, and component reliabilities of .90, .95, .98, and .99?

A) under 0.83

B) at most 0.90

C) 0.955

D) no less than .99

E) none of the above

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

32) A system is composed of three components A, B, and C. All three must function for the system to function. There are currently no backups in place. The system has a reliability of 0.966. If a backup is installed for component A, the new system reliability will be

A) unchanged

B) less than 0.966

C) less than 0.998

D) greater than 0.966

E) none of the above

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

33) A system has three components in series with reliabilities 0.9, 0.7, and 0.5. System reliability is

A) 0.315

B) 0.500

C) 0.700

D) 0.900

E) 2.100

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

34) A system has three components in parallel with reliabilities 0.9, 0.7, and 0.5. System reliability is

A) 0.315

B) 0.700

C) 0.900

D) 0.985

E) 2.100

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

35) Components A, B, and C are connected in series. Component D is connected in parallel to component B. Which of the following statements is true?

A) The system works only if A works, B or C works, and D works.

B) Component B must work for the system to work.

C) The system works when A works, C, works, and either B or D works.

D) Components B and C are backups to A.

E) The system works if D works, and any of A, B, or C works.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

36) A job consists of a series of three tasks. Task 1 is performed correctly 98% of the time, task 2 is performed correctly 99% of the time, and task 3 is performed correctly 97% of the time. The reliability of this job is

A) 91.27%

B) 94.11%

C) 97.00%

D) 98.00%

E) 99.00%

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

37) As the number of components in a system connected in a series decreases, all other things being equal, the reliability of the system usually

A) increases

B) stays the same

C) decreases

D) increases, then decreases

E) decreases, then increases

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

38) A product has three components, A, B, and C, with reliabilities of 0.95, 0.98, and 0.995. Engineers intend to put a redundant component A that has reliability 0.70. With this change, system reliability will

A) fall by 20%

B) fall by 10% or less

C) rise

D) cannot determine from the information provided

E) none of the above

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

39) What is the reliability of the three components connected in series shown below?

A) 0.799425

B) at least 0.85

C) 0.91333

D) 0.95000

E) 2.79

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

40) For the system shown below, the reliability is

A) 0.50000

B) 0.71280

C) 0.80000

D) 0.85536

E) 3.49000

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

41) Ten high-technology batteries are tested for 200 hours each. One failed at 20 hours; all others completed the test. FR(%) is __________ and MTBF is __________.

A) 10%; 1/1820

B) 90%; 1/1820

C) 10%; 1820 hours

D) 10%; 1980 hours

E) cannot calculate from information provided

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-3

42) Ten high-technology batteries are tested for 200 hours each. One failed at 50 hours; all others completed the test. FR(%) is __________ and FR(N) is __________.

A) 10%; 1/1850

B) 10%; 1/2000

C) 25%; 1850 hours

D) 90%; 1/2000

E) Indeterminate; no standard deviation is given.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-3

43) Ten high-technology batteries are tested for 200 hours each. One failed at 20 hours; another failed at 140 hours; all others completed the test. FR(%) is __________ and MTBF is __________.

A) 20%; 880 hours

B) 10%; 1980 hours

C) 20%; 1760 hours

D) cannot calculate from information provided

E) 80%; 920 hours

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-3

44) MTBF measures the average

A) calendar time between failures

B) operating time between failures

C) number of failures per unit time

D) number of operations between failures

E) downtime per breakdown

Diff: 2

Topic: Reliability

Objective: LO17-3

45) A system is composed of four parts, J, K, L, and M. All four must function for the system to function. The four component reliabilities are .99, .98, .992, and .998. The designers are considering putting a .80 reliable backup at K. This backup will change the system reliability from __________ to __________.

A) 0.9762 to 0.9605

B) 0.9605 to 0.9762

C) 0.9605 to some smaller value

D) cannot be determined

E) none of the above

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

46) Suppose that a process is comprised of multiple components, each having a 75% success rate. What is the change in reliability going from a series layout to a parallel layout if the process has 5 components?

A) 0%

B) 100%

C) 76.2%

D) -76.2 %

E) unable to determine

Diff: 2

Topic: Reliability

Objective: LO17-2

47) A two component process has a 81% success rate in series and a 99% success rate in parallel. If each component has the same reliability, what is the reliability of an individual component?

A) 50%

B) 90%

C) 99%

D) none of the above

E) unable to determine

Diff: 2

Topic: Reliability

Objective: LO17-2

48) The normal distribution is an appropriate model of

A) the high initial failure rates of product, machine, or processes

B) system reliability where components are connected in series

C) system reliability where components are connected in parallel

D) failures of products, machines, or processes that have "settled in"

E) the full cost view of maintenance

Diff: 2

Topic: Maintenance

Objective: LO17-4

49) Infant mortality refers to which one of the following examples?

A) high frequency on the left side of the MTBF distribution

B) failure of items used in the nursery ward of a hospital

C) failure of products with a very short life cycle

D) market failure of brand new products

E) high failure rate often encountered in the very early stages of the lifetime of a product

Diff: 2

Topic: Maintenance

Objective: LO17-4

50) How is MTBF related to FR(N)?

A) MTBF is measured in hours, while FR(N) is measured in years.

B) MTBF is normally distributed, with FR(%) as its mean and FR(N) as its standard deviation.

C) MTBF is the reciprocal of FR(N).

D) Both MTBF and FR(N) increase when breakdown maintenance is replaced by preventive maintenance.

E) MTBF and FR(N) are unrelated concepts.

Diff: 2

Topic: Reliability

Objective: LO17-4

51) A machine that has passed the phase of early failures exhibits a normal distribution of failures. The smaller the standard deviation of this distribution

A) the more expensive is preventive maintenance

B) the more likely this machine is a candidate for preventive maintenance

C) the shorter is the time interval between breakdowns

D) the more likely this machine will break down

E) the more likely this machine will be maintained by a breakdown maintenance policy

Diff: 2

Topic: Maintenance

Objective: LO17-4

52) Which one of the following statements about maintenance is true?

A) The optimal degree of preventive maintenance is associated with zero breakdowns.

B) Breakdown maintenance is proactive.

C) Preventive maintenance is reactive.

D) Preventive maintenance is limited to keeping machinery and equipment running.

E) Human resources are a major component of effective maintenance management.

Diff: 2

Topic: Maintenance

Objective: LO17-4

53) The process that involves repair on an emergency or priority basis is known as

A) breakdown maintenance

B) emergency maintenance

C) failure maintenance

D) preventive maintenance

E) priority maintenance

Diff: 2

Topic: Maintenance

Objective: LO17-4

54) As a firm's maintenance commitment increases,

A) the breakdown maintenance costs increase and the preventive maintenance costs decrease

B) both the breakdown maintenance costs and the preventive maintenance costs decrease

C) the breakdown maintenance costs decrease and the preventive maintenance costs increase

D) both the breakdown maintenance costs and the preventive maintenance costs increase

E) None of the above is true.

Diff: 2

Topic: Maintenance

Objective: LO17-5

55) An oil change is to__________ maintenance as a broken alternator is to __________ maintenance.

A) preventive, breakdown

B) breakdown, preventive

C) preventive, preventive

D) breakdown, breakdown

E) none of the above

Diff: 2

Topic: Maintenance

Objective: LO17-4

56) Infant mortality in electronics follows which kind of distribution?

A) normal

B) negative exponential

C) exponential

D) random

E) one-sided normal distribution

Diff: 2

Topic: Maintenance

Objective: LO17-5

57) Suppose that maintenance is deemed cost effective. Which is most likely true if the cost of maintenance is very expensive?

A) high standard deviation in MTBF

B) low standard deviation in MTBF

C) low Cost to Repair

D) repairs carry little non-monetary consequences

E) none of the above

Diff: 2

Topic: Maintenance

Objective: LO17-5

58) A manager is holding the total maintenance cost curves for two scenarios, one being breakdown maintenance and the other full cost of breakdowns. Which of the following should he notice going from the breakdown maintenance based total cost to the full cost of breakdowns curve?

A) total cost is decreased

B) optimal point is moved to the left

C) optimal point is moved to the right

D) preventative maintenance cost slope increased

E) none of the above

Diff: 2

Topic: Maintenance

Objective: LO17-6

59) As far as maintenance costs are concerned,

A) for low levels of maintenance commitment, breakdown maintenance costs exceed preventive maintenance costs

B) for low levels of maintenance commitment, preventive maintenance costs exceed breakdown maintenance costs

C) for high levels of maintenance commitment, breakdown maintenance costs exceed preventive maintenance costs

D) preventive maintenance is always more economical than breakdown maintenance

E) All of the above are true.

Diff: 2

Topic: Maintenance

Objective: LO17-4

60) For a machine to be a good candidate for preventive maintenance

A) the consequences of failure must exceed the cost of preventive maintenance and the MTBF distribution must have a large standard deviation

B) the consequences of failure must exceed the cost of preventive maintenance and the MTBF must be relatively low

C) the consequences of failure must exceed the cost of preventive maintenance and the MTBF distribution must have a relatively low standard deviation

D) the consequences of failure must exceed the cost of preventive maintenance and the MTBF must be relatively high

E) the consequences of failure must be relatively unknown and, therefore, risky

Diff: 2

Topic: Maintenance

Objective: LO17-4

61) Which one of the following is not necessary to identify the optimal maintenance policy?

A) historical data on maintenance costs

B) cost of performing the analysis

C) breakdown probabilities

D) breakdown occurrences

E) repair times

Diff: 2

Topic: Maintenance

Objective: LO17-5

62) Which of the following costs tend to be ignored in determining the optimal maintenance policy?

A) expected breakdown costs

B) preventive maintenance costs

C) the costs associated with various levels of commitment to maintenance

D) cost of low morale

E) all of the above

Diff: 2

Topic: Maintenance

Objective: LO17-5

63) DuLarge Marine manufactures diesel engines for shrimp trawlers and other small commercial boats. One of their CNC machines has caused several problems. Over the past 30 weeks, the machine has broken down as indicated below.

What is the expected number of breakdowns per week?

A) 1

B) 2

C) 6

D) 10

E) 30

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

64) DuLarge Marine manufactures diesel engines for shrimp trawlers and other small commercial boats. One of their CNC machines has caused several problems. Over the past 30 weeks, the machine has broken down as indicated below. Each time the machine breaks down, the firm loses an average of $3,000 in time and repair expenses.

What is the expected breakdown cost per week?

A) $1,000

B) $2,000

C) $6,000

D) $10,000

E) $60,000

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

65) DuLarge Marine manufactures diesel engines for shrimp trawlers and other small commercial boats. One of their CNC machines has caused several problems. Over the past 30 weeks, the machine has broken down as indicated below. Each time the machine breaks down, the firm loses an average of $3,000 in time and repair expenses. If preventive maintenance were implemented, it is estimated that an average of only one breakdown per week would occur. The cost of preventive maintenance is $1,000 per week.

What is the weekly total maintenance cost of this program?

A) $1,000

B) $3,000

C) $4,000

D) $6,000

E) $8,000

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

66) When depot service is compared to operator maintenance,

A) operator maintenance is slower than depot service

B) competence is higher, but costs may also be higher, with depot service

C) depot service is often the weak link in the chain because of the lack of specific training

D) depot service occurs on-site, while operator maintenance occurs off-site

E) depot service is better for systems connected in parallel, while operator maintenance is preferred for systems connected in series

Diff: 2

Topic: Maintenance

Objective: LO17-7

67) Which of the following increase as repairs move from the maintenance department to the depot service?

A) cost

B) replacement time

C) quality

D) employee ownership

E) A, B, and C

Diff: 2

Topic: Maintenance

Objective: LO17-5

68) Autonomous maintenance occurs when

A) employees are empowered to observe, check, adjust, clean, and notify

B) a remote computer system signals the need for breakdown maintenance

C) a remote computer system signals the need for preventative maintenance

D) employees perform their own breakdown maintenance

E) none of the above

Diff: 2

Topic: Maintenance

Objective: LO17-7

69) Which of the following is true regarding total productive maintenance (TPM)?

A) TPM is concerned with machine operation, not machine design.

B) Field service and depot service perform virtually all maintenance and repair activities.

C) Operators run their machines, but maintenance departments maintain them.

D) TPM reduces variability through employee empowerment and excellent maintenance records.

E) TPM views maintenance and repair as tactical issues, not strategic ones.

Diff: 2

Topic: Total productive maintenance

Objective: no LO

70) Techniques for enhancing maintenance can include

A) simulation of breakdowns from prolonged use

B) expert systems that aid in problem-solving

C) automated sensors that warn when preventative maintenance is required

D) A and C

E) A, B, and C

Diff: 2

Topic: Techniques for enhancing maintenance

Objective: LO17-5

71) __________ consists of all activities involved in keeping a system's equipment in working order.

Diff: 1

Topic: The strategic importance of maintenance and reliability

Objective: no LO

72) __________ is the probability that a machine part or product will function properly for a specified time under stated conditions.

Diff: 1

Topic: The strategic importance of maintenance and reliability

Objective: no LO

73) __________ is the expected time between a repair and the next failure of a component, machine, process, or product.

Diff: 2

Topic: Reliability

Objective: LO17-3

74) The inverse of the mean time between failures is the __________.

Diff: 2

Topic: Reliability

Objective: LO17-3

75) __________ is the use of a component in parallel to raise reliabilities.

Diff: 2

Topic: Reliability

Objective: LO17-1

76) __________ is a plan that involves routine inspections, servicing, and keeping facilities in good repair to prevent failure.

Diff: 2

Topic: Maintenance

Objective: LO17-4

77) __________ is the failure rate early in the life of a product or process.

Diff: 2

Topic: Maintenance

Objective: LO17-4

78) The __________ takes into account such costs as deteriorated customer relations and lost sales.

Diff: 2

Topic: Maintenance

Objective: LO17-4

79) __________ combines total quality management with a strategic view of maintenance from process equipment design to preventive maintenance.

Diff: 2

Topic: Increasing repair capabilities

Objective: no LO

80) Describe how Orlando Utilities Commission obtains competitive advantage through its maintenance practices.

Diff: 2

Topic: Global company profile

Objective: no LO

81) What is the role of people, especially empowered employees, in an effective maintenance strategy?

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: no LO

82) Identify the two reliability tactics and the two maintenance tactics.

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: no LO

83) Define reliability.

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: no LO

84) Define maintenance.

Diff: 2

Topic: The strategic importance of maintenance and reliability

Objective: LO17-4

85) What is the impact on system reliability of adding parts or components in parallel?

Diff: 1

Topic: Reliability

Objective: LO17-1

86) Increasing the number of parts or components in a product tends to reduce its reliability. Why is this true only when adding components in series?

Diff: 2

Topic: Reliability

Objective: LO17-1

87) Explain carefully how redundancy improves product reliability.

Diff: 2

Topic: Reliability

Objective: LO17-1

88) Why is it that many cases of infant mortality of products are not due to product failure?

Diff: 2

Topic: Maintenance

Objective: LO17-4

89) "High reliability can be achieved in a product without having high reliability in the component parts. In fact, any reliability target, no matter how high, can be achieved with only mediocre parts, so long as enough of them are present." Discuss; an example may help.

Diff: 2

Topic: Reliability

Objective: LO17-1

90) What is FR(N)? How is it calculated? How are FR(N) and MTBF related?

Diff: 2

Topic: Reliability

Objective: LO17-1

91) What is breakdown maintenance?

Diff: 1

Topic: Maintenance

Objective: LO17-4

92) Explain why a small standard deviation of the MTBF distribution makes a product, machine, or process a good candidate for preventive maintenance while a large standard deviation does not.

Diff: 2

Topic: Maintenance

Objective: LO17-5

93) Why is it that many cost curves associated with maintenance rarely consider the full cost of a breakdown?

Diff: 2

Topic: Maintenance

Objective: LO17-4

94) Is there an optimal amount of preventive maintenance? What caution should be exercised before calculating this optimal amount?

Diff: 2

Topic: Maintenance

Objective: LO17-4

95) How do many electronic firms deal with infant mortality in their products?

Diff: 2

Topic: Maintenance

Objective: LO17-4

96) Under what conditions is preventive maintenance likely to be appropriate?

Diff: 2

Topic: Maintenance

Objective: LO17-5

97) What is the primary concept of total productive maintenance (TPM)? List the other elements of total productive maintenance.

1. Designing machines that are reliable, easy to operate, and easy to maintain

2. Emphasizing total cost of ownership when purchasing machines

3. Developing preventive maintenance plans that utilize best practices of operators, maintenance departments, and depot service, and

4. Training workers to operate and maintain their own machines

Diff: 2

Topic: Total productive maintenance

Objective: no LO

98) How do expert systems improve maintenance systems?

Diff: 2

Topic: Techniques for enhancing maintenance

AACSB: Use of IT

Objective: no LO

99) Ten high-intensity bulbs are tested for 100 hours each. One failed at 40 hours; all others completed the test. Calculate FR(%) and FR(N).

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

100) Ten high-intensity bulbs are tested for 100 hours each. One failed at 10 hours; all others completed the test. Calculate FR(%), FR(N) and MTBF.

MTBF = 910 hours

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

101) Ten high-intensity bulbs are tested for 100 hours each. One failed at 40 hours; another failed at 70 hours; all others completed the test. Calculate FR(%), FR(N), and MTBF.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

102) A product is composed of a series connection of four components with the following reliabilities. What is the reliability of the system?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

103) Given the following data, find the expected breakdown cost. The cost per breakdown is $200.

Expected number of breakdowns = (0 * .10) + (1 * .24) + (2 * .20) + (3 * .36) + (4 * .10) = 2.12

Expected cost of breakdowns = 2.12 * $200 = $424.

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

104) Given the following data, find the expected breakdown cost. The cost per breakdown is $100.

Expected number of breakdowns per month = (0 * .10) + (1 * .40) + (2 * .46) +

(3 * .04) = 1.44; Expected cost of breakdowns = 1.44 * $100 = $144

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

105) Great Southern Consultants Group's computer system has been down several times over the past few months, as shown below.

Each time the system is down, the firm loses an average of $400 in time and service expenses. They are considering signing a contract for preventive maintenance. With preventive maintenance, the system would be down on average only 0.5 per month. The monthly cost of preventive maintenance would be $200 a month. Which is cheaper, breakdown or preventive maintenance?

Expected number of breakdowns per month = (0 * .45) + (1 * .10) + (2 * .20) + (3 * .20) +

(4 * .05) = 1.30; Expected cost of breakdowns per month = 1.30 * $400 = $520

Preventive maintenance cost per month = (.5 * $400) + $200 = $400; Preventive maintenance is more cost-effective.

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

106) A system has four components in a series. What is the reliability of the system?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

107) A system consists of four components in series. The reliability of each component is 0.96. What is the reliability of the system?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

108) A system has six components in series. Each component has a reliability of 0.99. What is the reliability of the system?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

109) Tiger Island Fabricators, which builds offshore oil platforms, has been experiencing problems with its profiling machine, a computer-driven device that cuts the ends of pipe so that it can be welded to another pipe, as shown in the data below.

Each time a machine breaks down, the company loses about $3,000. If the company implements preventive maintenance, it will be able to reduce the number of breakdowns to one per month. Preventive maintenance costs would be $500 a month. Is preventive maintenance a cost-effective option?

Expected number of breakdowns = (0 * .10) + (1 * .10) + (2 * .10) + (3 * .30) + (4 * .35) +

(5 * .05) = 2.85; Expected cost of breakdowns per month = 2.85 * $3,000 = $8,550; Cost of preventive maintenance = (1 * $3,000) + $500 = $3,500. It is about three times more expensive to suffer breakdowns than to perform preventive maintenance.

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

110) The diagram below identifies the elements of service as provided by a soft drink vending machine. Each element has an estimate of its own reliability, independent of the others. What is the reliability of the "system"?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

111) Century Digital Phone advertises phone battery life (on standby) of up to three days. The standard deviation is thought to be five hours. Tina Talbot, an employee at CDP, tested 10 of these batteries for 72 hours. One failed at 40 hours; one failed at 62 hours; one failed at 70 hours. All others completed the test. Calculate FR(%), FR(N), and MTBF.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-3

112) The Everstart is a battery with an intended design life of 72 months. Stephanie Bradley recently put five of these batteries through accelerated testing (the company couldn't wait six years) to simulate failure patterns. The test results had one failure at 26 months, one failure at 32 months, one failure at 50 months, and one failure at 62 months. Calculate FR(%), FR(N), and MTBF.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-3

113) The academic service commonly referred to as "registration" consists of several smaller components: advising, registration for courses, fee assessment, financial aid calculations, and fee payment. Each of these modules operates independently and has some probability of failure for each student. If the five probabilities which accompany these services are 95%, 90%, 99%, 98%, and 99%, what is the "reliability" of the entire product from the student's perspective–the probability that all five will work according to plan?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

114) A simple electrical motor has three components: windings, armature, and housing. These three components have reliabilities of .9998, .9992, and .9999. There is no possibility of redundant parts. What is the reliability of the motor? Round your answer to four decimal places.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

115) A simple electrical motor has three components: windings, armature, and housing. These three components have reliabilities of .97, .992, and .999. There is no possibility of redundant parts. The motor must have an overall reliability of 0.980, according to the product line manager who will use the motor as an input. What would you do to redesign the motor to meet this specification? Discuss, including a recalculation to meet the standard.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

116) A product has four components A, B, C, and D. The finished product must have a reliability of .95. The first three components come from a supplier, and have reliabilities of .99, .98, and .995. The fourth component is being designed now. What must the reliability of component D be in order to meet the product reliability condition?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

117) A product has three components X, Y, and Z. X has reliability of 0.991; Y has reliability of 0.993. If Z has reliability of 0.991, what is the reliability of the entire product? Can Z be redesigned to be reliable enough for the entire product to have reliability of 0.99? Explain.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

118) A component must have reliability of .9925. Two technologies are available for this component: one produces a component with .999 reliability at a cost of $2000. Another produces a component with .73 reliability at a cost of $450. Which is cheaper: one high quality component or a parallel set of inferior components?

Diff: 3

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

119) General Grant must send orders to General Butler. Carrier pigeons are the medium of choice. A single pigeon has a .7 probability of arriving at the proper destination in a timely fashion. How many pigeons, each carrying an identical set of orders, must Grant send in order for him to have 98% confidence that the orders reached General Butler?

Diff: 3

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

120) Which product design below has the higher system reliability?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

121) Which product design below has the higher system reliability?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

122) Consider a product that is "settled in." Its MTBF distribution has been found to be normal with a mean of 10,000 hours and a standard deviation of 100 hours. What is the probability of a breakdown before 8,000 hours? Before 9,000 hours? Would you prefer a policy of preventive maintenance, or a policy of breakdown maintenance, on this product? Explain your choice.

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

123) Suppose that a car mechanic offers you a deal that for the next 3 years any breakdowns will be covered, so long as you bring your car in for $50 preventative maintenance sessions each month. If you predict the likelihood of a breakdown being 25% without the maintenance, how much must a breakdown cost for you to prefer the preventative maintenance?

Breakdown cost = $7200.

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

124) Suppose that a manufacturing plant is considering contracting out some preventative maintenance work. For $2000 each year a firm would cover all breakdowns free of charge and provide preventative maintenance. Two other options exist that entail the use of regular employees however. The first is to skip preventative measures and simply fix breakdowns, which occur at a rate of 2/year. Each breakdown costs about $750 to fix. The final option is to divert excess labor capacity to preventative measures, which reduces the chance of a breakdown per year by Y% given X hours of preventative maintenance subject to Y=10X-X^2. If each preventative maintenance hour costs $50, which option should the firm choose?

Diff: 3

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

125) Suppose that a three stage process had reliability ratings of .7, .8, and .9 at each station and that a failure at any station represented a failure for the entire process. If each station is given a redundant check with .9 reliability, what is the increase in system reliability?

New (1-.3*.1)(1-.2*.1)(1-.1^2)=.941

New-Old= .437 or 43.7% improvement

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

126) Suppose that a three stage process in a nuclear reactor had reliability ratings of .98 at each station and that only one stage needed to be successful for the process to work. If the plant wants to establish 6-sigma standards, what % reliable redundant controls need to be added to each station.

3.4/1000000=(.02*(1-X))^3 or X= .248 or 24.8% reliable

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

127) A manufacturing firm wants to apply 6-sigma standards to its automated tolerance-check process. Suppose that each scanner makes the correct decision only 50% of the time, however only 1 correct decision by any scanner makes the entire process a success. How many scanners are needed to ensure 6-sigma quality?

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

128) A product design team is preparing to build a new doohickey. A doohickey consists of one A module, one B module, and one C module. There are different versions of these modules available in the company's design library. For example, there are two choices for A: A1 is .99 reliable, while A2 is .975 reliable. The table below details the choices available, along with the cost of each choice.

Help the design team by selecting the least costly version of a doohickey that has system reliability of at least .96. Draw a schematic of your finished design.

(I) A10.99 * B10.995 * C10.98 = 0.96535 meets the reliability specification but costs $23.

(II) A20.975 * B20.992 * C10.98 = 0.947856 costs $15 but does not meet the specification.

There are a dozen design alternatives which have no redundant parts. There are many more choices with one or more redundancies built in. The reliability of A2 + B2 is 0.975 * 0.992 = 0.9672, which means that redundancies at C are an option.

(III) A20.975 * B20.992 * C2+C20.99 = 0.957528 costs $16 but does not meet the test.

(IV) A20.975 * B20.992 * C1+C30.992 = 0.95946 costs $15.25 but does not meet the test.

(V) A20.975 * B20.992 * C2+C3+C3+C30.9936 = 0.96101 costs $14.25 and meets the test. It is possible that even cheaper solutions exist. The schematic for this design appears below.

Diff: 3

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2

129) Consider a product that is "settled in." Its MTBF distribution has been found to be normal with a mean of 1,000 hours and a standard deviation of 250 hours. What is the probability of a breakdown before 750 hours? Before 500 hours? Would you prefer a policy of preventive maintenance, or a policy of breakdown maintenance, on this product? Explain your choice.

Diff: 2

Topic: Maintenance

AACSB: Analytic Skills

Objective: LO17-6

130) A high school senior is seeking admission into her state's flagship university. The admission requirements are as follows. The student must meet at least ONE of the criteria A, B, C. The student must meet criterion D. These criteria are detailed below. And the student must file a complete application, file a medical form, and pay an application fee by a stated date.

A: score a composite 28 on the ACT exam

B: have a high school GPA of 3.0 or greater

C: place in the top ten percent of the high school class

D: complete all courses in the state-mandated "core college preparatory" curriculum (CCPC); OR complete all but one course in CCPC with a 3.5 GPA on all CCPC courses taken.

Using the tools of reliability analysis with redundancy, translate these conditions into the appropriate reliability schematic.

Diff: 2

Topic: Reliability

AACSB: Analytic Skills

Objective: LO17-2