The chief design engineer for Colonial Warning Systems wants to know the reliability of a two-lamp device intended to warn the operator of potential problems with a commercial steam kettle.One (either)lamp is to be lit if steam pressure drops below the desired level,and two (both)are to be lit if temperature drops below a desired level.His supplier estimates that a lamp has a failure rate of .2 per hour of operation,and a mean wear-out time of seven years with a standard deviation of eight months.If the pressure drops below the desired level,what is the probability the system will perform reliably for one hour?
A).04
B).4
C).6
D).64
E).96

Question

Quizplus · Accepted Answer

The probability that one lamp will not fail in one hour is 1 - 0.2 = 0.8. Since only one lamp needs to work for the system to perform reliably when the pressure drops, the probability that at least one lamp works is 1 - (probability both lamps fail) = 1 - (0.2 * 0.2) = 0.96.

The Chief Design Engineer for Colonial Warning Systems Wants to Know