CQE Measurement Systems Analysis 2 — Questions and Answers
Question 1: According to the AIAG MSA manual, a Gauge R&R result is generally considered acceptable when % Gauge R&R is:
- Less than 10% of total variation, with no exceptions
- Between 10% and 30% for all critical characteristics
- Less than 30%, where under 10% is ideal and 10–30% may be acceptable based on application (Correct answer)
- Greater than 30% when the gauge is used for monitoring rather than acceptance
Correct answer: Less than 30%, where under 10% is ideal and 10–30% may be acceptable based on application
The AIAG MSA manual classifies % Gauge R&R under 10% as acceptable, 10–30% as marginal (may be acceptable based on importance and cost), and over 30% as generally unacceptable.
Question 2: The 'number of distinct categories' (ndc) in a Gauge R&R study indicates:
- The total number of operators who participated in the study
- The number of measurements taken per part per operator per trial
- The number of non-overlapping categories the gauge can reliably distinguish within process variation (Correct answer)
- The number of parts selected for inclusion in the study design
Correct answer: The number of non-overlapping categories the gauge can reliably distinguish within process variation
The ndc represents how many statistically distinct groups can be detected within the process variation; a value of 5 or more is required for the gauge to be considered adequate.
Question 3: The %P/T ratio in measurement systems analysis compares:
- Total process variation to total measurement system variation
- Measurement system variation to the engineering specification tolerance (Correct answer)
- Operator variation to equipment variation within a Gauge R&R study
- Process standard deviation to the gauge's minimum detectable increment
Correct answer: Measurement system variation to the engineering specification tolerance
The %P/T (Precision-to-Tolerance) ratio expresses the gauge's measurement variation as a percentage of the specification tolerance, showing how much of the tolerance band is consumed by measurement error.
Question 4: The standard design for a crossed Gauge R&R study per AIAG MSA guidelines typically includes:
- 5 operators, 5 parts, and 5 trials each for a total of 125 measurements
- 10 operators, 10 parts, and 1 trial each for a total of 100 measurements
- 2 or 3 operators, 10 parts, and 2 or 3 measurement trials per part per operator (Correct answer)
- 1 operator, 25 parts, and 4 trials each to focus on repeatability
Correct answer: 2 or 3 operators, 10 parts, and 2 or 3 measurement trials per part per operator
AIAG recommends 2–3 operators, 10 parts, and 2–3 trials, providing sufficient data to estimate both repeatability and reproducibility while remaining practical to conduct.
Question 5: Compared to the Average and Range method, the ANOVA method in Gauge R&R analysis provides the additional ability to:
- Reduce the total number of parts required for a valid study
- Detect and quantify the operator-by-part interaction effect (Correct answer)
- Automatically correct for measurement bias during the analysis
- Eliminate outlier measurements from the data before analysis
Correct answer: Detect and quantify the operator-by-part interaction effect
The ANOVA method partitions variance into repeatability, reproducibility, and the operator-by-part interaction term, providing richer information about how operator and part effects combine.
Question 6: When parts are destroyed during the measurement process, the appropriate MSA study design is:
- A standard crossed Gauge R&R study with a larger sample size
- A nested (destructive) Gauge R&R study where parts are nested within operators (Correct answer)
- A bias and linearity study using a certified reference standard
- A stability study conducted over multiple production shifts
Correct answer: A nested (destructive) Gauge R&R study where parts are nested within operators
A nested (destructive) Gauge R&R is used when parts cannot be re-measured; different but similar parts are assigned to each operator so repeatability and reproducibility can still be estimated.
Question 7: When % Gauge R&R falls in the marginal range of 10–30%, the key factor in deciding acceptability is:
- Whether the gauge manufacturer provides a certificate of accuracy for that range
- Whether the gauge has been in continuous service for more than one calibration interval
- The importance of the characteristic, cost of gauge improvement, and risk of measurement error (Correct answer)
- Whether the gauge meets ISO/IEC 17025 laboratory accreditation requirements
Correct answer: The importance of the characteristic, cost of gauge improvement, and risk of measurement error
AIAG MSA guidance states that for marginal gauges, the decision depends on practical factors including the criticality of the characteristic, the cost of a better gauge, and the risk posed by measurement-driven errors.
CQE Measurement Systems Analysis 2
According to the AIAG MSA manual, a Gauge R&R result is generally considered acceptable when % Gauge R&R is: