CPT Quality Assurance & Process Control 2 — Questions and Answers
Question 1: A control chart shows several consecutive points trending upward toward the upper control limit. This pattern is called a:
- Random variation
- Run or trend (Correct answer)
- Outlier
- Attribute defect
Correct answer: Run or trend
A series of consecutive points moving in the same direction is called a run or trend, indicating a non-random shift in the process.
Question 2: Which sampling method involves dividing a population into groups and randomly selecting samples from each group?
- Simple random sampling
- Systematic sampling
- Stratified sampling (Correct answer)
- Convenience sampling
Correct answer: Stratified sampling
Stratified sampling divides the population into subgroups (strata) and samples from each, ensuring representation across all groups.
Question 3: The process capability ratio Cpk differs from Cp because Cpk accounts for:
- Sample size
- Process centering relative to specification limits (Correct answer)
- Measurement system error
- Operator skill level
Correct answer: Process centering relative to specification limits
Cpk measures capability while accounting for how well the process mean is centered between the specification limits, unlike Cp which only measures spread.
Question 4: A fishbone diagram is primarily used to:
- Plot defect frequency over time
- Identify root causes of a quality problem (Correct answer)
- Set upper and lower control limits
- Calculate process yield
Correct answer: Identify root causes of a quality problem
A fishbone (Ishikawa) diagram organizes potential causes of a problem into categories to help identify root causes.
Question 5: In acceptance sampling, the Acceptable Quality Level (AQL) represents:
- The maximum defect rate the customer will tolerate
- The worst quality level still acceptable to the producer (Correct answer)
- The point where sampling inspection is discontinued
- The percentage of lots rejected by the plan
Correct answer: The worst quality level still acceptable to the producer
AQL is the maximum percent defective that can be considered satisfactory as a process average for acceptance sampling purposes.
Question 6: Which type of measurement error occurs when the same operator gets different results measuring the same part repeatedly?
- Bias
- Linearity
- Repeatability (Correct answer)
- Reproducibility
Correct answer: Repeatability
Repeatability is the variation in measurements taken by the same operator using the same gauge on the same part under the same conditions.
Question 7: A poka-yoke device is best described as:
- A statistical process control chart
- An error-proofing mechanism that prevents or detects mistakes (Correct answer)
- A calibration standard for measuring instruments
- A quality cost tracking system
Correct answer: An error-proofing mechanism that prevents or detects mistakes
Poka-yoke (mistake-proofing) devices are designed to prevent errors from occurring or to immediately detect them if they do occur.
CPT Quality Assurance & Process Control 2
A control chart shows several consecutive points trending upward toward the upper control limit.
This pattern is called a: