**Sensitivity Reproducibility Accuracy of Measurement Precision of Measurement Definition of Gage R&R Gage R&R –Repeatability Reproducibility**

There is much confusion on measurement terminology. There are four characteristics to examine in a gage system.

** Sensitivity**

The gage should be sensitive enough to detect differences in measurement as slight as one-tenth of the total tolerance specification or process spread, whichever is smaller. Inadequate discrimination will affect boththe accuracy and precision of an operator’s reported values.

**Reproducibility**

The “reliability” of the gage system or similar gage systems to reproduce measurements. The reproducibility of a single gage is customarily checked by comparing the results of different operators taken at different times. Gage reproducibility affects both accuracy and precision.

**Accuracy of Measurement**

•Broken down into three components:

1. Stability: the consistency of measurements over time.

2. Accuracy: a measure of the amount of bias in the system.

3. Linearity: a measure of the bias values through the expected range of measurements.

**Precision of Measurement**

•Precision, aka Measurement Variation, can be broken down into two components:

1. Repeatability (Equipment variation): variation in measurements under exact conditions.

2. Reproducibility (Appraiser variation): variation in the average of measurements when different operators measure the same part.

**Definition of Gage R&R**

•Gage R&R is a method of determining:

–Repeatability

–Reproducibility

**Gage R&R –Repeatability**

The term “repeatability”refers to:

•The inherent variability of the measuring system

•Variation that occurs when repeated measurements are made of the same item under absolutely identical conditions–Same operator–Same setup–Same units–Same environmental conditions

**Gage R&R –Reproducibility**

The term “reproducibility”refers to:•The variation that results when different conditions are used to make the measurements–Different operators–Different setups–Different units–Different environmental conditions–Different measurement systems

**•If the measurement system fails to pass analysis, before collecting data:**

**–Fix gage**

**–Fix measurement system**

**–Train measurement takers**

At the conclusion of the Measurement System Analysis, the Project Team should know that:

-The measurement system is capable of gathering data that accurately reflects variation in the process

– If there is measurement error, how big it is and a method of accounting for it

-Measurement increments are small enough to show variation

-Sources of measurement error have been identified

Example of Study Gage R&R: You can read results with below logic in mind:

If the Total Gage R&R contribution in the %Study Var column (% Tolerance, %Process) is:

- Less than 10% – the measurement system is acceptable.
- Between 10% and 30% – the measurement system is acceptable depending on the application, the cost of the measuring device, cost of repair, or other factors.
- Greater than 30% – the measurement system is unacceptable and should be improved.