See also: https://asqrrd.org/tech-spot-sample-cre-questions-part-28/
1. An engineer feels confident that the failure probability on a new electro magnetic relay is less than 0.01. The specifications require, however, only that p < 0.04. How many units must be tested without failure to prove with 95% confidence that p < 0.04?
A. 65
B. 73
C. 74
D. 75
2. Let’s assume a hurricane eye’s probability of entering Palm Beach County is 0.1 per season. How many
hurricanes should you expect in a decade? What is the probability of 4 or more hurricanes in a decade?
A. 0.0001
B. .001
C. 0.4
D. 3.85×10-6
3. The probability that a golfer hits the ball onto the green if it is windy as he strikes the ball is 0.4, and the corresponding probability if it is not windy as he strikes the ball is 0.7. The probability that it will be windy is 0.3. Find the probability that he hits the ball onto the green,
A. 0.61
B. .0.39
C. 0.49
D 0.12
4. If the CDF for times to failure is Find the failure rate as a function of time.
A. 𝜆(𝑡)= 2/((𝑡+20) )
B. 𝜆(𝑡)= 3/((𝑡+20) )
C. 𝜆(𝑡)= 2/((𝑡+10) )
D 𝜆(𝑡)= 1/((𝑡+10) )
5. The MTBF for truck tire punctures is 150,000 miles. A truck with 10 tires carries 1 spare.
What is the probability that the spare will be used on a 10,000-mile trip?
A. 0.0645
B. .0.9355
C. 0.0323
D 0.87
6. Suppose that a device undergoing accelerated testing can be described by a Weibull distribution with a shape factor of β = 2.0. Under accelerated test conditions, with an acceleration factor (AF) = 5.0, 50% of the devices are found to fail during the first month. Under normal operating conditions, estimate how long the device will last before the failure probability reaches 10%. (i.e.B10 life ).
A. 1 month
B. 2 months
C. 3 months
D. 4 months
7. At rated voltage, a microcircuit has been estimated to have an MTTF of 20,000 hr. An accelerated life test is to be carried out to verify this number. It is known that the microcircuit life is inversely proportional to the cube of the voltage. At least 10% of the test circuits must fail before the test is terminated if we are to have confidence in the result. If the test must be completed in 30 days, at what percentage of the rated voltage should the circuits be tested?
A. 1.25
B. 2.7
C. 3.6
D 1.43
8. Fatigue specimens were put on test. They were all tested to failure and the failure times were 150, 85, 250, 240, 135, 200, 240, 150, 200, and 190 hours. What is the B10 life?
A. 110h
B. 120h
C. 98h
D. 140h
9. A failure PDF for an appliance is assumed to be a
Weibull distribution with β= 4.622 and η = 5.44 years.
What is the design life at a reliability of 90%?
A. 4.55 yrs
B. 1.78 yrs
C. 3.36 yrs
D 2.56 yrs
10. Consider the following PDF:
Determine the mean and variance
A. 0.333
B.0.577
C. 0.666
D. 0.75