# Measurement Error - How to determine what is acceptable?

#### Mohd.Z

##### Registered
Hello Everyone,

I need some guidance her,

In a gage R&R Study, what should be the Ratio of the Gage variation (Equipment Variation (%EV)) to the Parts variation (%PV)?

How can we say that the conducted Gage R&R Study is good,
1) If the variation of the Gage is High?
of
2) If the Variation of the Parts is high

Can Anyone Plese help me here.
Thank You.

#### Miner

##### Forum Moderator
The typical guidance given is that the total R&R as a % of the study variation (%SV), the tolerance (%Tol), or process variation (%PV) is < 10% (ideal); 11 - 30% (may be acceptable depending on the application); > 30% (unacceptable).

If you are using the gauge for process control (i.e., SPC), use %PV (ideal if you have capability data) or %SV . Alternatively, use ndc (> 5).
If you are using the gauge for inspection to tolerance, use %Tol.
If you want to identify the major source of measurement error, use %contribution to focus improvement efforts.

#### Bev D

##### Heretical Statistician
Super Moderator
If you are new to Gage R&R - then I suggest reading up on the topic as it - like so many things - is somewhat complicated. Both Miner and I have some good resources in the resources section of this site. You might also try reading some of Donald Wheeler’s articles (they are free at quality digest .com)

Definition MPEE - Maximum Permissible Error for Length Measurement Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 0
Measurement Error on pure Graphite Coating on Tubes - To Error or Not to Error Using Minitab Software 7
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Dr. Wheeler on "How Measurement Error Affects the Four Ways We Use Data" Measurement Uncertainty (MU) 0
P Measurement Error Requirements - 99% or 99.73% spread to represent the 'full' spread? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
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