# TECH SPOT: SAMPLE CRE QUESTIONS (PART 7)

1. Three components in parallel have mean times to failure of 50, 60, & 70 hrs respectively. The mean repair times are 30, 40 & 50 hrs respectively. What is the steady state availability, assuming all non-failed components remain operating during system downtime?

a. 0.8891 b. 0.2187 **c. 0.9375** d. 0.0419

2. The Reliability Qualification Test (RQT) is designed primarily to:

a. Disclose weak parts

b. Simulate in-service evaluations of the delivered item.

** c. Assure that minimum acceptable reliability requirements have been met.**

d. Disclose design deficiencies under simulated conditions.

3.How can linear acceleration be verified, where

I. the Weibull slope under accelerated and normal conditions should be the same,

II. The failure mode should be the same

** a. Only I above** b. Only II above c. I & II above d. none of these

4. Components A,B, and C are exponentially distributed with mean times to failure of 40 hrs, 60 hrs, and 75 hours. If these components are in series, what is the system hazard function?

a. .051 **b. .055** c. .571 d. none of these

5. Designing non-confusing displays to ease interaction of humans under stress is a method for reducing:

a. Job satisfaction b. Performance problems

c. The root cause of many problems **d. High-stress error**

6. The probability of an accident for the head event “H” to the right is:

a. .1125 ** b. .0689 ** c. .1100 d. none of theses

7. Acceptance tests are:

a. Performed to demonstrate that prime hardware meets design

specification requirements including mission environments

** b. Conducted to verify conformance to quality requirements and to determine acceptability of hardware**

c. Performed on preliminary to prototype hardware to determine design and performance parameters

d. None of the above

8. The primary **reason **that non-conforming material
should be identified and segregated is:

a. so that the cause of non conformity can de determined

b. to provide statistical information for the “zero defects” program

** c. so it cannot be sued in production without proper authorization**

d. to obtain samples of poor workmanship for use in the company’s training program

9. Based on subgroups of n=10 the grand average is 10 and the average subgroup s=0.5. Compute the lower

control limit for the s chart.

a. 0.051 **b. 0.142** c. 0.243 d. 0.247

10. The process engineer believes that a modified process will produce the same results as the existing process, while costing less. The existing process was stable with a mean of 50 mm and s=0.06. The process engineer ran 25 units with the new process. The control chart for the 25 units was stable, the sample mean =49 and s=0.05. Compute the value of the appropriate statistic to test the null hypothesis that the variance of the modified process is the same as the variance of the original process.

a. 0.97 b. 4.31 **c. 16.67** d. 21.22

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