CQE Measurement Systems Analysis 1 — Questions and Answers
Question 1: In a Gauge R&R study, 'repeatability' refers to variation caused by:
- Different operators using the same measurement system on the same part
- The same operator using the same measurement system repeatedly on the same part (Correct answer)
- Differences between multiple measurement instruments in a facility
- Environmental factors such as temperature and humidity changes
Correct answer: The same operator using the same measurement system repeatedly on the same part
Repeatability (equipment variation) is the variation that occurs when one operator uses the same gauge to measure the same part multiple times under identical conditions.
Question 2: In measurement systems analysis, the difference between accuracy and precision is best described as:
- Accuracy measures consistency of results; precision measures closeness to the true value
- Accuracy measures closeness to the true value; precision measures consistency of repeated results (Correct answer)
- Accuracy and precision are equivalent concepts in quality engineering
- Accuracy applies only to variable data; precision applies only to attribute data
Correct answer: Accuracy measures closeness to the true value; precision measures consistency of repeated results
Accuracy reflects how close the average measurement is to the true or reference value, while precision describes how consistently repeated measurements agree with each other.
Question 3: 'Bias' in a measurement system is formally defined as:
- The spread of measurements across the full operating range of a gauge
- The variation observed between different operators measuring the same part
- The difference between the observed average measurement and the accepted reference value (Correct answer)
- The inconsistency of a single operator's repeated measurements on the same part
Correct answer: The difference between the observed average measurement and the accepted reference value
Bias is the systematic offset between the average of measured values and the reference or true value, indicating a consistent tendency to over-measure or under-measure.
Question 4: 'Linearity' in a measurement system describes:
- The consistency of bias values across the full operating range of a gauge (Correct answer)
- The straightness and uniformity of scale markings on a measuring instrument
- The ability to take measurements along a straight-line path without deviation
- The correlation between measurement speed and resulting accuracy
Correct answer: The consistency of bias values across the full operating range of a gauge
Linearity assesses whether the gauge's bias remains constant or changes systematically as the measured value changes across the gauge's operating range.
Question 5: 'Stability' in a measurement system refers to:
- The mechanical durability of a gauge under heavy, repeated use
- The change in bias of a measurement system over time when measuring the same master part (Correct answer)
- The ability of a gauge to remain calibrated under varying operator techniques
- The consistency of a gauge's discrimination level across its measurement range
Correct answer: The change in bias of a measurement system over time when measuring the same master part
Stability (also called drift) is the total variation in measurements obtained with a single gauge on the same master or reference part over an extended time period.
Question 6: The minimum recommended resolution (discrimination) for a measurement instrument should be:
- Equal to the product specification tolerance
- Equal to the process standard deviation
- At least one-tenth of the total tolerance or process variation being measured (Correct answer)
- Greater than the total reproducibility variation of the gauge
Correct answer: At least one-tenth of the total tolerance or process variation being measured
The AIAG MSA manual recommends that gauge resolution be at least one-tenth of the tolerance range or process variation so that meaningful differences between parts can be detected.
Question 7: The primary purpose of a calibration system in a quality management program is to:
- Ensure all measuring equipment is operated only by certified technicians
- Prevent equipment from being used beyond its scheduled replacement date
- Provide traceability of measurement results to national or international standards (Correct answer)
- Standardize measurement procedures uniformly across all product lines
Correct answer: Provide traceability of measurement results to national or international standards
A calibration system maintains measurement accuracy by establishing an unbroken traceability chain linking measurements back to primary standards maintained by organizations such as NIST.
CQE Measurement Systems Analysis 1
In a Gauge R&R study, 'repeatability' refers to variation caused by: