Gauge R&R Study

Table of Contents

What is a Gauge R&R Study?

A Gauge R&R study evaluates how much of the observed measurement variation is due to the measurement system (gauge and operators) versus actual differences between parts. It uses ANOVA to decompose variation into Repeatability (same operator, same part) and Reproducibility (different operators, same part).

1Define the Study

Set the number of operators (2-5), parts (2-10), trials (2-5), and the process tolerance (USL - LSL). A common design is 3 operators, 10 parts, and 3 trials.

2Enter Measurements

Each operator measures each part multiple times (trials). Enter values in the grid organized by operator tabs. All cells must be filled before analysis.

3Review Analysis

The tool computes %GRR, %EV, %AV, part variation, and the number of distinct categories (ndc). An ANOVA table shows the statistical significance of operator and interaction effects.

4Save & Export

Save your study results and download a PDF report. Saved studies can be accessed later via the results link.

Understanding Results

ACCEPTABLE %GRR below 10%. The measurement system is reliable for this tolerance.

MARGINAL %GRR between 10% and 30%. May be acceptable depending on the application and cost of improvement.

UNACCEPTABLE %GRR above 30%. The measurement system consumes too much of the tolerance. Investigate gauge condition and operator training.

Key Terms

%EV: Equipment Variation (Repeatability) - variation when the same operator measures the same part repeatedly.
%AV: Appraiser Variation (Reproducibility) - variation between different operators measuring the same part.
%GRR: Gauge R&R - combined gauge and operator variation as a percentage of tolerance.
ndc: Number of Distinct Categories - how many groups the measurement system can reliably distinguish. 5 or more is ideal.

Tip:

Use 10 parts that span the full range of expected production variation. Randomize the measurement order so operators do not remember previous readings.