CPT Quality Practices & Measurement 2 — Questions and Answers
Question 1: What does a control chart's 'upper control limit' (UCL) represent?
- The maximum allowed specification
- Three standard deviations above the process mean (Correct answer)
- The highest acceptable customer tolerance
- The target production value
Correct answer: Three standard deviations above the process mean
The UCL is set at three standard deviations above the process mean, indicating the boundary beyond which variation is considered non-random.
Question 2: Which sampling method selects every nth item from a production run?
- Random sampling
- Stratified sampling
- Systematic sampling (Correct answer)
- Cluster sampling
Correct answer: Systematic sampling
Systematic sampling selects every nth item at fixed intervals throughout the production run.
Question 3: What is the purpose of a fishbone (Ishikawa) diagram in quality management?
- Track defect counts over time
- Identify root causes of a problem (Correct answer)
- Compare two production processes
- Calculate process capability
Correct answer: Identify root causes of a problem
A fishbone diagram visually maps potential causes of a problem, organized by categories like machine, method, material, and manpower.
Question 4: A gauge with a resolution of 0.001 inch is used to measure a part tolerance of ±0.005 inch. This gauge resolution is considered:
- Too coarse for the measurement
- Adequate for the measurement (Correct answer)
- Too fine and introduces error
- Irrelevant to the measurement task
Correct answer: Adequate for the measurement
A gauge resolution of 0.001 inch can distinguish increments much smaller than the ±0.005 inch tolerance, making it adequate.
Question 5: Which quality cost category includes the cost of inspecting incoming raw materials?
- Internal failure costs
- External failure costs
- Appraisal costs (Correct answer)
- Prevention costs
Correct answer: Appraisal costs
Incoming inspection is an appraisal activity — it evaluates product or process quality before further processing.
Question 6: On a p-chart, what does 'p' stand for?
- Process performance index
- Proportion of defective units in a sample (Correct answer)
- Process mean value
- Number of defects per unit
Correct answer: Proportion of defective units in a sample
A p-chart monitors the proportion (fraction) of defective items in successive samples of varying or fixed size.
Question 7: What action should a technician take when a measurement falls exactly on the upper control limit of a control chart?
- Immediately shut down the line
- Treat it as in-control but monitor closely (Correct answer)
- Scrap all parts produced since last sample
- Recalibrate the measuring instrument
Correct answer: Treat it as in-control but monitor closely
A single point on the control limit is technically still in-control, but the technician should watch for additional signals suggesting a process shift.
CPT Quality Practices & Measurement 2
What does a control chart's 'upper control limit' (UCL) represent?