# TECH SPOT: Sample CRE questions

1. Which answer BEST describes the events and operating conditions an item experiences from mission initiation to completion? The events may include the research and development phase, product manufacturing, warehousing, and so on, to mission completion.

A. Operational readiness; **B. Mission profile**; C. Design adequacy; D. Mission reliability

2. What is System Effectiveness, if Operational Readiness is 0.89, Design Adequacy is 95%, Availability is 99%, Maintainability is 0.93, and Mission Reliability is 0.99? Ebeling, p 149

A. 0.763; B. 0.881; **C. 0.837**; D. 0.820

3. Which of the following functions are normally accepted reliability engineering tools?

I. Failure probability density function; II. Failure rate function; III. Reliability function; IV. Conditional reliability function; V. Mean life function.

A. I and II only; B. I, II and III only; C. I, II, III and IV only; **D. I, II, III, IV and V **

4. An airline maintains a fleet of 4-engine aircraft. Its maintenance records show that on the average an engine fails 3 times in 10,000 operating hours with normal preventive maintenance. What is the Poisson distributed probability that 2 or more engines on an aircraft will fail during a typical flying period of 8 hours?

A. 0.000034; B. 0.0000034; **C. 0.0000029**; D. 0.000029

5. For the exponential model, the reliability at mean time to failure is about:

**A. 37 percent****;** B. 50 percent; C. 67 percent; D. 73 percent

6. A plastics plant operates 8 extruders producing plastic film. Production volume requirements cannot be met if less than 6 extruders are operating. There is a .30 probability that a machine stopping malfunction will occur. What is the probability that 6 extruders can remain operating throughout the day?

A. 0.5783; B. 0.4482; **C. 0.5518**; D. 0.8059

7. A system is made up of four independent components in series each having a failure rate of .005 failures per hour. If time to failure is exponential, then the reliability of the system at 10 hours is:

**A. 0.8187**; B. 0.8860; C. 0.9512; D. 0.9802

8. What is the reliability of this system?

Where component reliabilities are: A. 0.80; B. 0.95; C. 0.82; D. 0.85; E. 0.75

A. 0.10; B. 0.90; **C. 0.95**; D. 0.04

9. Which method is used to predict new device reliability during its early design stage?

A. Burn-in method; B. Part stress analysis method; **C. Parts count method**; D. Accelerated testing method

10. Which of the following forms of reliability data will BEST provide valuable information on product usage and reliability?

A. In-house test results. B. Independent lab results. **C. Field support data****.** D. Quality control data.

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