Deck 4: Extension: Reliability

Question 1

Availability cannot be increased without improving the time between breakdowns.

Answer 1

False

Question 2

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

Answer 2

True

Question 3

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

Answer 3

True

Question 4

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) .95
B) .9975
C) .9025
D) .9205
E) .9795

Question 5

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?

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

Question 6

Redundancy is often more cost-effective than increasing individual component reliability.

Question 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. What is the overall system reliability?

A) .99
B) .95
C) .94
D) .90
E) Cannot be determined with this information.

Question 8

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.

Question 9

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

Question 10

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

Question 11

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?

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

Question 12

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 __________.

A) increasing; reliability
B) reducing; time required for repair
C) reducing; reliability
D) reducing; reparability
E) increasing; time required for repair