Before interpreting the process, verify that the measurement system produces data that are good enough for the decision you need to make. AIAG emphasises that better measurement data improve decision quality; MSA is broader than Gage R&R alone.
Separates repeatability, reproducibility, operator×part interaction and part-to-part variation. Includes %Study Var, %Contribution, ndc and optional %Tolerance.
Open Gage R&R →Continuous data · multiple appraisers · same partsEstimates systematic difference from a reference value and the confidence interval for mean bias.
Open Bias →One reference · repeated measurementsChecks whether bias remains constant across the measurement range or changes with characteristic size.
Open Linearity →Multiple references across the operating rangeTracks a check standard over time for drift, centre shifts and changes in precision.
Open Stability →Time-ordered data · baseline + monitoringEvaluates appraiser consistency, between-appraiser agreement and agreement with a known standard.
Open Attribute Agreement →Nominal/attribute data · appraisers · repeated trialsAIAG Measurement Systems Analysis, 4th edition is the primary automotive reference. AIAG describes the manual as a basis for assessing measurement-system quality and recognising opportunities for improvement. For public formulas and verifiable explanations we also use NIST/SEMATECH — Gauge R&R and Minitab technical documentation. QAPP does not reproduce the AIAG manual and does not automatically certify compliance.
An MSA result should not be read in isolation. Instrument resolution, sampling strategy, part selection, appraisers, fixturing, method, environment, calibration and the decision purpose can all change interpretation. Final criteria must be confirmed against customer requirements and measurement-use risk.