Interactive Calculator – Impact of Gage R&R on Process Capability

Use this Interactive Calculator to Estimate True Process Capability

  1. 1. Enter your specification limits – LSL & USL (Must be a 2 -sided spec.)
  2. 2. Use the slider to select your Observed Process Capability
  3. 3. Use the slider to select your Precision To Tolerance Ratio (or Gage R&R % based on Tolerance)
  4. 4. Get a normal chart for your process, like the one below – showing your Observed Process Normal Curve, and your True Process Normal Curve

Normal Curves Examples For Process Capability

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Impact of Gage R&R on the Capability Index Cp

Calculator #1 – Remove The Impact of Gage R&R (based on Tolerance) To Estimate Actual Process Capability

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Is this a poor process? – How Gage R&R impacts Process Capability

A non-technical explanation of the impact of gage variation on process capability.

To get the most out of this article you should:

  • – Understand a histogram
  • – Understand Specification Limits
  • – Understand the concept of Process Capability

Is this a poor process?

Let’s say we run a machine and produce 100 parts. Then, we measure each part and …

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Process and Gage R&R Simulation

Using the Process and Gage R&R Simulation

This calculator simulates a Process and a Gage by taking a sample of 100 values and plotting them on a scatter chart (or X-Y plot).

Process – You can play with the Capability of the True Value Process using the ‘ Change Underlying Process Capability Index ‘ Slider.

Gage R&R – You can change the Gage R&R Variation using the ‘ Change Gage R&R (as % of Tolerance) ‘ Slider.

Process Output – True Value + Gage Error = Observed Value, so these two values combine to give you the Observed Process – i.e. the Measured Process.

Example Scatter Plot

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What is Measurement System Analysis?

What is Measurement System Analysis – Overview Video

The full article covers the basics of Measurement System Analysis, including Bias, Stability, Linearity, Repeatability & Reproducibility …

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High Repeatability? – Why it may not be a Gage Problem

What is repeatability?

This is the definition of Repeatability from Automotive Industry Action Group Measurement System Analysis Guide Book:

“Repeatability is the variation in measurements obtained with one measurement instrument when used several times by one appraiser while measuring the identical characteristic on the same part. This is the inherent variation or capability of the equipment itself.” …

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Gage R&R Formulas


What is it?

Gage R&R Formulas

Repeatability – Equipment Variation (EV%) Repeatability is the variation that occurs when repeated measurements are made by the same operator. This assumes that the operator uses a consistent technique, and that the part is consistent. If these assumptions are true, then the Repeatability Variation is inherent in the measuring instrument itself. EV\% = \frac{Repeatability\ Std. Dev.}{Total\ Variation\ Std. Dev.} = \frac{EV\sigma}{TV\sigma}
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Book Review: Design and Analysis of Gauge R&R Studies

Design and Analysis of Gauge R&R Studies: Making Decisions with Confidence Intervals in Random and Mixed Anova Models (ASA-SIAM Series on Statistics and Applied Probability)
by Richard K. Burdick, Connie M. Borror, Douglas C. Montgomery
ASA-SAM Series on Statistics and Applied Probability 2005



An applied Statistician, or someone who needs an in-depth …

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Book Review: Concepts for R&R Studies 2nd Ed.

Concepts for R&R Studies, Second Edition
by Larry B. Barrentine
ASQ Quality Press (February 29, 2012)


Someone who needs a brief overview of the practical and statistical sides of Gage R&R, using the minimum of math. The appendices do cover the Math in a bit more detail.


Could you conduct a simple gage …

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Why you should ignore the AIAG MSA Guidelines for % Gage R&R, and what to do instead


  • Review of the AIAG Measurement System Analysis Guidelines
  • Modeling the Process and Measurement System
  • Running Some Scenarios Through The Model
  • What to do instead

Review of the AIAG MSA Guidelines

Let’s start with a review of the Guidelines:
From AIAG Measurement Systems Analysis Reference Manual – 3rd Edition
Chapter II Section D Analysis of the Results
“For measurement systems whose purpose is to analyze a process, a general rule of thumb for measurement system acceptability is as follows:
Under 10 percent error – generally considered to be an acceptable measurement system …

Observed Process Capability Measurement System Precision To Tolerance Ratio (%) Business Implications (in terms of the risk of producing out-of-spec. product)
2.0 10% No action needed – good process, room for drift. The chart below shows how close the lines are
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