PSY 330 Human Factors
5/1/00
Day 2-21
Effects of Redundancy on Reliability
uActive Redundancy: Both components operate all the time but only one is needed.
uFailure occurs only when both fail or (EP1)*(EP2)
uThus reliability is:RS = 1 - P(1-RI)
l
lExample: Use two components and both components have a reliability of 0.90.
lIn a series| Rs = .9*.9 = .81 (above)
lRedundant| Rs = 1-(1-.9)2  = .99
lTwo redundant components in a series|
l Rs = .99*.99 = .98