1. Measurement System Analysis
An evaluation of the measurement system MUST be undertaken to ensure effective
analysis of any subsequent data generated for a given process/product characteristic
Measurement error is a statistical term meaning the net effect of all sources of
measurement variability that cause an observed value to deviate from the true value
Both process and measurement variability must be evaluated and improved together
If we work on process variability first and our measurement variability is large, we can
never conclude that the improvement made was significant, or correct
Observed Value = True Value +/- Measurement Error
True Variability = Process Variability + Measurement Variability

2. Types of Measurement Errors
Measurement System Bias - Calibration Study
Measurement System Variation - GRR Study
µ total = µ process +/- µ measurement
σ2 total = σ2 process σ2 measurement

3. Observed Process Variation
Sources of Variation
Observed Process Variation
Actual
Process
Variation
Measurement
Variation
Long-term
Process
Variation
Short-term
Process
Variation
Variation
within a
Sample
Variation
due to
Operators
Variation
due to
Gage
Reproducibility
Accuracy
Repeatability
Stability
Linearity

4. Measurement system Error
Sources of Variation
Measurement system Error
Precise
Accurate
Repeatability
Reproducibility
Accuracy can be taken care by Calibration
Precision can be taken care by GRR
Accuracy
Stability
Linearity

5. Component of GRR Study 1 2 1 2 1 2 Trial Reading #1 3 4 3 4 3 4 5 6 5
Difference leads
to Reproducibility 1 2 1 2 1 2
Trial
Reading #1 3 4 3 4 3 4 5 6 5 6 5 6
Difference leads to
Repeatability
Six Parts / Conditions 1 2 1 2 1 2
Trial
Reading #2 3 4 3 4 3 4 5 6 5 6 5 6
Operator A
Operator B
Operator C

6. Methods of Performing GRR: ANOVA Method
ANOVA not only separates the equipment & operator variation, but also elaborates
on combined effect of operator & part
ANOVA uses the ‘standard deviation’ instead of ‘range’, & hence gives a better
estimate of the measurement system variation
ANOVA also may not need the ‘tolerance’ value as an input