Q
AshToolbox Quality Lean Six Sigma Suite
Advanced Category: Process Capability & Measurement (MSA) • ~9 min read

Gage R&R Study (Crossed ANOVA Method)

Statistically qualify measurement instruments and determine whether inspection variation masks product quality.

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Q:

What are the AIAG acceptance criteria for %GRR and Number of Distinct Categories (ndc)?

Under AIAG MSA-4 guidelines: %GRR < 10%: Acceptable measurement system.
10% ≤ %GRR ≤ 30%: Marginal system; may be acceptable based on application criticality.
%GRR > 30%: Unacceptable system; gage must be improved or calibrated.
ndc ≥ 5: Required to distinguish part-to-part variation effectively.

%GRR (Study Var)3.67%<10% Ideal, >30% Fail
Distinct Categories (ndc)38ndc ≥ 5 Required
Measurement SystemAcceptableAIAG MSA-4 Guideline

Two-Way Crossed ANOVA Table

SourceDFSSMSFP-Val
Parts274.167837.083966751.0000.0000
Operators20.04780.023943.0000.0020
Operator × Part40.00220.00060.1250.9697
Repeatability (Equipment)90.04000.0044——
Total1774.25784.3681——

Two-Way Crossed ANOVA Gage Repeatability & Reproducibility

Crossed ANOVA decomposes total measurement error into:

  • Repeatability (Equipment Variation): Inherent variation observed when one appraiser measures the identical part multiple times using the same gage.
  • Reproducibility (Appraiser Variation): Variation between different operators using the same instrument.
  • Part-to-Part Variation: Real product dimensional spread across manufactured units.
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Engineering Disclaimer: These tools and calculators are intended for engineering analysis, educational study, and operational guidance. They do not constitute formal regulatory certification (such as medical, aerospace flight-critical, or statutory safety filings) without independent audit and sign-off by a certified Quality Engineer or Six Sigma Black Belt. AshToolbox is not affiliated with, sponsored by, or endorsed by AIAG, ISO, ASQ, or any standards body.

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