ch4s Student: _ 1. Reliability is the probability that a product or system will function when activated. True False 2. If a system depends on two subsystems functioning when activated, the reliability of that system is equal to the lower reliability of the two subsystems. True False 3. Redundancy is often more costeffective than increasing individual component reliability. True False 4. Availability cannot be increased without improving the time between breakdowns. True False 5. Product reliability involves both shortterm and longterm perspectives. True False 6. A system consists of two components, each of which must activate if the system is to activate. One component has a reliability of .99. The other has a reliability of .95. What is the overall system reliability? A. .99 B. .95 C. .94 D. .90 E. Cannot be determined with this information 7. A system consists of two components, each of which must activate if the system is to activate. One component has a reliability of .99. The other has a reliability of .95. The components are independent of one another with respect to reliability. What is the overall system reliability? A. .99 B. .95 C. .94 D. .90 E. Cannot be determined with this information 8. An electrical appliance will not work unless component QK does. Component QK's reliability is 0.95. Every other part of the appliance is 100% reliable. What would the reliability of the appliance be if a backup QK were added? A. .95 B. .9975 C. .9025 D. .9205 E. .9795 9. The time between failures for an electrical appliance is exponentially distributed with a mean of 25 months. What is the probability that the next failure won't occur before 30 months have elapsed? A. Not in excess of .2 B. In excess of .2 but not in excess of .3 C. In excess of .3 but not in excess of .4 D. In excess of .4 but not in excess of .6 E. In excess of .6 10. Waygate's residential internet modem works well but is sensitive to powerline fluctuations. On average, this product hangs up and needs resetting every 200 hours. On average about 45 minutes is needed to reset this product. What is this product's availability? A. Not in excess of .75 B. In excess of .75 but not in excess of .8 C. In excess of .8 but not in excess of .9 D. In excess of .9 but not in excess of .95 E. In excess of .95 ch4s Key 1. Reliability is the probability that a product or system will function when activated. TRUE The higher the probability, the more reliable the product or system AACSB: Reflective Thinking Blooms: Remember Difficulty: Easy Learning Objective: 04s01 Define reliability Stevenson Chapter 04S #1 Topic Area: Quantifying Reliability 2. If a system depends on two subsystems functioning when activated, the reliability of that system is equal to the lower reliability of the two subsystems. FALSE The reliability is the probability that both subsystems will activate AACSB: Reflective Thinking Blooms: Understand Difficulty: Easy Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #2 Topic Area: Quantifying Reliability 3. Redundancy is often more costeffective than increasing individual component reliability. TRUE Increasing individual component reliability is often much more expensive than simply adding redundancy AACSB: Reflective Thinking Blooms: Remember Difficulty: Medium Learning Objective: 04s03 Explain the purpose of redundancy in a system Stevenson Chapter 04S #3 Topic Area: Quantifying Reliability 4. Availability cannot be increased without improving the time between breakdowns. FALSE Reducing the amount of time required to repair a product is also a way of increasing availability AACSB: Reflective Thinking Blooms: Understand Difficulty: Medium Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #4 Topic Area: Availability 5. Product reliability involves both shortterm and longterm perspectives. TRUE Reliability involves whether a product will work at a point in time, as well as the probability that it will work for a given length of time AACSB: Reflective Thinking Blooms: Remember Difficulty: Easy Learning Objective: 04s01 Define reliability Stevenson Chapter 04S #5 Topic Area: Quantifying Reliability 6. A system consists of two components, each of which must activate if the system is to activate. One component has a reliability of .99. The other has a reliability of .95. What is the overall system reliability? A. .99 B. .95 C. .94 D. .90 E. Cannot be determined with this information Whether these components' reliabilities are independent of one another is not specified here AACSB: Analytic Blooms: Apply Difficulty: Hard Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #6 Topic Area: Quantifying Reliability 7. A system consists of two components, each of which must activate if the system is to activate. One component has a reliability of .99. The other has a reliability of .95. The components are independent of one another with respect to reliability. What is the overall system reliability? A. .99 B. .95 C. .94 D. .90 E. Cannot be determined with this information The system reliability is the product of the two component reliabilities AACSB: Analytic Blooms: Apply Difficulty: Easy Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #7 Topic Area: Quantifying Reliability 8. An electrical appliance will not work unless component QK does. Component QK's reliability is 0.95. Every other part of the appliance is 100% reliable. What would the reliability of the appliance be if a backup QK were added? A. .95 B. .9975 C. .9025 D. .9205 E. .9795 The reliability is .95 + [(1 .95)*.95] AACSB: Analytic Blooms: Apply Difficulty: Medium Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #8 Topic Area: Quantifying Reliability 9. The time between failures for an electrical appliance is exponentially distributed with a mean of 25 months. What is the probability that the next failure won't occur before 30 months have elapsed? A. Not in excess of .2 B. In excess of .2 but not in excess of .3 C. In excess of .3 but not in excess of .4 D. In excess of .4 but not in excess of .6 E. In excess of .6 T/MTBF is 1.2. From the chart, the reliability is 0.3012 AACSB: Analytic Blooms: Apply Difficulty: Medium Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #9 Topic Area: Quantifying Reliability 10. Waygate's residential internet modem works well but is sensitive to powerline fluctuations. On average, this product hangs up and needs resetting every 200 hours. On average about 45 minutes is needed to reset this product. What is this product's availability? A. Not in excess of .75 B. In excess of .75 but not in excess of .8 C. In excess of .8 but not in excess of .9 D. In excess of .9 but not in excess of .95 E. In excess of .95 MTBF is 200 and MTTR is .75. This leads to an availability of 0.996 AACSB: Analytic Blooms: Apply Difficulty: Medium Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #10 Topic Area: Availability ch4s Summary Category # of Questions AACSB: Analytic AACSB: Reflective Thinking Blooms: Apply Blooms: Remember Blooms: Understand Difficulty: Easy Difficulty: Hard Difficulty: Medium Learning Objective: 04s01 Define reliability Learning Objective: 04s02 Perform simple reliability computations Learning Objective: 04s03 Explain the purpose of redundancy in a system Stevenson Chapter 04S 10 Topic Area: Availability Topic Area: Quantifying Reliability ... Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #10 Topic Area: Availability ch4s Summary Category # of Questions AACSB: Analytic AACSB: Reflective Thinking... AACSB: Reflective Thinking Blooms: Remember Difficulty: Easy Learning Objective: 04s01 Define reliability Stevenson Chapter 04S #1 Topic Area: Quantifying Reliability 2. If a system depends on two subsystems functioning when activated, the reliability of that system is equal to ... Blooms: Understand Difficulty: Easy Learning Objective: 04s02 Perform simple reliability computations Stevenson Chapter 04S #2 Topic Area: Quantifying Reliability 3. Redundancy is often more costeffective than increasing individual component reliability.