CPE Quality Control & Reliability Engineering 3

Question 1

Process capability index Cp is calculated using which formula?

Accepted Answer

Cp = (USL - LSL) / 6σ

Answer

Cp = (USL − LSL) / 6σ, where USL and LSL are the upper and lower specification limits and σ is the process standard deviation; a Cp ≥ 1.33 is generally considered capable.

Question 2

How does the Cpk index differ from the Cp index in process capability analysis?

Accepted Answer

Cpk accounts for process centering relative to the specification limits while Cp does not

Answer

Cpk = min[(USL − X̄)/3σ, (X̄ − LSL)/3σ], incorporating how centered the process mean is within the specification limits, unlike Cp which only measures spread.

Question 3

What is the purpose of a Gauge Repeatability and Reproducibility (Gauge R&R) study?

Accepted Answer

To quantify the variation in measurements attributed to the measurement system itself

Answer

A Gauge R&R study separates measurement variation into repeatability (equipment variation) and reproducibility (appraiser variation), ensuring the measurement system is adequate relative to process variation.

Question 4

Weibull analysis in reliability engineering is primarily used for which purpose?

Accepted Answer

Modeling and analyzing failure time data to estimate product life and failure patterns

Answer

Weibull analysis fits failure time data to the Weibull distribution to estimate parameters such as characteristic life and shape factor, enabling prediction of failure probabilities and remaining life.

Question 5

In reliability block diagrams (RBDs), components connected in series have what effect on overall system reliability?

Accepted Answer

System reliability is lower than the reliability of the least reliable component

Answer

For series systems, overall reliability = R1 × R2 × … × Rn; since each factor is less than 1, the product is always lower than the least reliable individual component.

(CPE) Certified Plant Engineer Practice Test

(CPE) Certified Plant Engineer Practice Test

CPE Quality Control & Reliability Engineering 3