5.3.2 Examples of Reliability
Calculations Using the Normal Distribution
126.96.36.199 Microwave Tube
A microwave transmitting tube has been observed to follow a
normal distribution with m = 5000 hours and s
= 1500 hours. Find the reliability of such
a tube for a mission time of 4100 hours and the hazard rate of one of these
tubes at age 4400 hours.
as found in Table 5.3-1. Remember P ( z >
-zi) = P ( z < zi) by symmetry of
the normal distribution.
where f(z = 0.4) was obtained from Table 5.3-2. Remember f(z)=f(-z) because of
the symmetry of the normal distribution.
188.8.131.52 Mechanical Equipment
A motor generator has been observed to follow a normal
distribution with m = 300 hours and s = 40 hours. Find the reliability of the motor generator
for a mission time (or time before maintenance) of 250 hours and the hazard
rate at 200 hours.
where P(z < -1.25) was interpolated from Table 5.3-1.
where f (z = 2.5) was found in Table 5.3-2.