Question

Device of type A is working properly without failures on average 1300hours, the standard deviation being 250 h. Time without failures is supposed to be normally distributed. The device is put to use at moment ?=0.

a) Determine the reliability of the device at moment t=1050 h. Give the answer as a decimal number in interval [0,1] (not as a percentage) with accuracy of three decimal places.

b) Determine the failure density and failure rate at moment t=1050h. Give the answers in unit of 1/h, without writing the unit, with accuracy of five decimal places.

c) Another type of device, type B, has mean time between failures 1500 hours. With this type of device the time without failures is exponentially distributed. If a system consists of three devices, one of type A and two of type B, then what is the probability that the system works properly without failures at least 1200 hours? Give the answer as a decimal number in interval [0,1] (not as a percentage) with accuracy of three decimal places.

Answer 1