# TECH SPOT: SAMPLE CRE QUESTIONS (Part 9)

1. The effects of failure rates on increased temperatures is called the:

a. Thermal model

b. Full scale Model

**c. Arrhenius Model **

d. Derating effects

2. Recognizing the nature of process variability, the process capability target is usually:

a. looser than product specifications

b. the same as product specifications

**c. tighter than product specifications **

d. not related to product specifications

3. (blank) software failure are the result of design errors.

a. **All **b. Most c. Many d. No

4. How can linear acceleration be verified?

a. with a probability plot

b. with a hazard plot

**c. either a. or b.**

None of the above

5. The purpose of derating parts is to:

a. Increase parts life

b. Enhance overall system reliability

c. Improve circuit design

**d. All of these**

6. A sequential test plan is graphically shown in the figure below. If the first 3 items tested fail, and the next 18 succeed, what is the status of the test?

a. Reject the null hypothesis

b. Accept the null hypothesis

**c. Continue testing **

d. None of these

7. Inherent of intrinsic reliability:

**a. is that reliability which can only be improved by design change**

b. can be improved only by an improvement in the state of the art

c. is that reliability estimated over stated period of time by a stated measurement technique.

d. is not an estimated reliability

8.An item has a constant failure rate of 50, and a constant repair rate of 22, what is the steady-state availability?

a. 0.983 b. 0.924 c. 0.815 **d. none of the these**

9. The failure rate for a carpet manufacturer is 3.7 per 1000 square yards. What is the probability of finding no defects in a random sample of 100 square yards.

a. 0.7145 **b. 0.6907 ** c. 0.9581 d. none of these

10. Given a shape parameter of 1.7 for the Weibull distribution, and assuming no failures, how long will 20 items have to be tested to give a reliability of 0.95 at t=100,000 with 90% confidence?

a. 119.329 **b. 160,896 ** c. 189,744 d. 276,901

Picture © B. Poncelet https://bennyponcelet.wordpress.com