CRE Life Data Analysis 2

Question 1

In Weibull analysis, a shape parameter (β) of exactly 1 indicates which failure behavior?

Accepted Answer

Constant failure rate (random failures)

Answer

When β = 1, the Weibull distribution reduces to the exponential distribution, which has a constant (memoryless) failure rate.

Question 2

Which method for parameter estimation minimizes the sum of squared deviations between observed and predicted reliability values on a probability plot?

Accepted Answer

Rank Regression on X (RRX)

Answer

Rank Regression on X (RRX) fits parameters by minimizing the horizontal (X-axis) squared residuals on a Weibull probability plot.

Question 3

A suspended (censored) test item in life data analysis is one that:

Accepted Answer

Was removed from test without failing

Answer

Suspended (right-censored) units are items removed from the test before failure, providing only a lower bound on their true failure time.

Question 4

The median rank formula (Benard's approximation) for the i-th failure out of n units is:

Accepted Answer

(i − 0.3) / (n + 0.4)

Answer

Benard's approximation for median ranks is F(i) ≈ (i − 0.3) / (n + 0.4), widely used for Weibull probability plotting.

Question 5

In a lognormal life distribution, the parameter σ (log-standard deviation) primarily controls:

Accepted Answer

The spread or dispersion of the distribution

Answer

In the lognormal distribution, σ is the scale parameter governing spread; a larger σ means greater variability in failure times.

(CRE) Certified Reliability Engineer Practice Test

(CRE) Certified Reliability Engineer Practice Test

CRE Life Data Analysis 2