Gage R&R (Measurement System Analysis)

Gage R&R quantifies how much observed variation comes from the measurement system versus genuine part differences. Answers whether the gauge can reliably distinguish good parts from bad.

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Step 1 — Provide your data

Crossed design: multiple operators each measure the same parts multiple trials.

Typical: 3 operators x 10 parts x 3 trials = 90 measurements.

Supports Excel Import, Sample Data Generator, and Manual Entry.

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Step 2 — Results

Variance components:

• Repeatability (EV) — same operator, same part variation
• Reproducibility (AV) — between-operator variation
• Gage R&R (GRR) — combined EV + AV
• Part-to-Part (PV) — genuine part variation

Percentage breakdowns (% study variation, % contribution)

ANOVA table — Operator, Part, Interaction, Repeatability

Number of Distinct Categories (NDC)

A UniversalChatBot is available for discussion.

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Statistical methods used

ANOVA method — two-factor crossed design (operators x parts with replicates).

Variance components derived from mean squares.

Acceptance criteria (AIAG):

% Gage R&R	Verdict
< 10%	Acceptable
10% - 30%	Marginal
> 30%	Unacceptable

NDC: floor(sqrt(2) * SD_part / SD_gageRR). Need NDC >= 5 for adequate discrimination.

Interpretation:

• High repeatability = gauge imprecise (fix/replace gauge)
• High reproducibility = operators differ (train/standardise)
• High part-to-part = good (real variation being detected)