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Exam 4: RELIABILITY – Static

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Question 1

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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 percent reliable. What would the reliability of the appliance be if a backup QK were added?

A)  0.95
B)  0.9975
C)  0.9025
D)  0.9205
E)  0.9795

F) B) and E)
G) A) and C)

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Question 2

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Suppose a given control unit fails, on average, every 12,000 hours. It takes an average of 900 hours to repair and reboot this unit. The repair/reboot procedures for this unit are being reconfigured. By how much would average repair/reboot time need to be reduced to increase availability by 5 percent (assuming the control unit's average life remains unchanged) ?

A)  not more than 200 hours
B)  more than 200 hours but not more than 400 hours
C)  more than 400 hours but not more than 600 hours
D)  more than 600 hours but not more than 800 hours
E)  more than 800 hours

F) C) and D)
G) B) and C)

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D

Question 3

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Waygate's residential Internet modem works well but is sensitive to power-line 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?

If a system depends on two subsystems functioning when activated, the reliability of that system is equal to that of the less reliable subsystem.

Product reliability involves both short-term and long-term perspectives.

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?

Availability cannot be increased without improving the time between breakdowns.

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?

If the average amount of time a product goes without failing decreased by some amount, that product's availability could nevertheless be maintained at previous levels by __________ its __________.

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 will not occur before 30 months have elapsed?

One way to increase overall reliability of a system is to add parts that increase redundancy in the system.

Reliability is frequently defined as the probability that a product or system will function when activated.