ILAC-g8:03/2009 - Reporting Results with Measurement Uncertainty

DietCokeofEvil

Trusted Information Resource
Anyone familar with this? We got hit with a big doozy for the beginning of 2012 involving reporting results with measurement uncertainty. I'm curious if anyone else is going through this.

Basically, from now on, we have to report a measurement uncertainty for each line item on our certifications. This isn't a problem- but what I don't like is that if your measurement result overlaps the limit, we are to state that it is impossible to state compliance or non-compliance. (IE- your initial result is within tolerance, but with the added measurement uncertainty- it goes over the upper or lower limit).

Any thoughts on this issue? We're trying to figure out how to explain this to the customers. Somehow, I don't think they're going to appreciate "We don't know" as an acceptable calibration result.

Thanks,
 

Hershal

Metrologist-Auditor
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Yes, you are correct about the customer perception. However, this is the very nature of uncertainty. This only seems to deal with statement of compliance to a specification however, so unless that is the requiement you should be able to simply report the measurement and the uncertainty. Make sure you become aware of ILAC P14, but note that it is going to hopefully have some work done on it this April.

If you have to state compliance to a specification, then paragraph 2.3 (c) provides the statement that you should likely use if the uncertainty exceeds the specification limit.
 

DietCokeofEvil

Trusted Information Resource
My question- we've been 17025 for a while- these changes are coming from our accrediting body with ILAC documentation. Neither of our competitors have the ILAC logo on their website- they are both A2LA. Is A2LA doing this as well?
 
D

dv8shane

Anyone familar with this? We got hit with a big doozy for the beginning of 2012 involving reporting results with measurement uncertainty. I'm curious if anyone else is going through this.

Basically, from now on, we have to report a measurement uncertainty for each line item on our certifications. This isn't a problem- but what I don't like is that if your measurement result overlaps the limit, we are to state that it is impossible to state compliance or non-compliance. (IE- your initial result is within tolerance, but with the added measurement uncertainty- it goes over the upper or lower limit).

Any thoughts on this issue? We're trying to figure out how to explain this to the customers. Somehow, I don't think they're going to appreciate "We don't know" as an acceptable calibration result.

Thanks,
If you employ guardbanding of the the specifications and the measurand falls within the guardbanded specifications you can still issue a conformance statement. Remember that your uncertainties are specified at a level of confidence of 95%% therefore by manipulating the specification (making it smaller as the TUR decreases http://assets.fluke.com/appnotes/calibration/ddncsl94.pdf) you can make the probability of false reject due to uncertainty fall within the necessary limits.
 
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D

dv8shane

My question- we've been 17025 for a while- these changes are coming from our accrediting body with ILAC documentation. Neither of our competitors have the ILAC logo on their website- they are both A2LA. Is A2LA doing this as well?
A2LA is a "member" of ILAC so even though the competitors do not display the logo I would think they would have to comply
 

Hershal

Metrologist-Auditor
Trusted Information Resource
My question- we've been 17025 for a while- these changes are coming from our accrediting body with ILAC documentation. Neither of our competitors have the ILAC logo on their website- they are both A2LA. Is A2LA doing this as well?

A2LA will have to answer that one. The US based ABs do have to work with ILAC documents, but more emphasis may be placed on some documents such as P14 and perhaps a bit less on others like G8 unless there is a reason to concentrate on it like reference to specifications. Additionally, each of the six have a position on the Z540.3 standard, which may vary a bit.

ILAC and Regionals like APLAC, in accordance with ISO/IEC 17011, can allow a little flexibility to the ABs for their respective market environments, so long as the rigor and oversight is equivalent to other Signatory bodies.

As for the ILAC symbol, A2LA is including the logo on newer accreditation certificates, but the labs have the option whether they place it on their cal certs/test reports or their website.

All six of the US based ABs that accredit labs (not Police forensics labs), and several non-US based ABs, sit on the same Committees at NCSLI and other venues, and the discussions like this come up at times. There are efforts to standardize some things, like scope expression, so customers can compare A2LA to L-A-B to IAS and so forth so customers can compare apples to apples.

Hope this helps.
 

DietCokeofEvil

Trusted Information Resource
Yes, you are correct about the customer perception. However, this is the very nature of uncertainty. This only seems to deal with statement of compliance to a specification however, so unless that is the requiement you should be able to simply report the measurement and the uncertainty. Make sure you become aware of ILAC P14, but note that it is going to hopefully have some work done on it this April.

If you have to state compliance to a specification, then paragraph 2.3 (c) provides the statement that you should likely use if the uncertainty exceeds the specification limit.



According to our accrediting body, we are required to state compliance, or our inability to state compliance. I have an email volley going back and forth between us and them where they do not even want us using the term "within uncertainty" as a calibration result because they find it to be misleading. In the 3 weeks since we have implemented this, we have lost customers because we are not able to tell them whether or not their gages are in tolerance. It is apparent to me that our competition is not following what we are being forced to follow.

We are not able to get a straight answer from our accrediting body about what their other calibration houses are doing to address the customer complaints regarding our new lack of reporting ability.

I'm not saying I disagree with this at all. I have always felt that more responsibility needed to be put on the customer to read their certifications and analyze the findings against their own acceptance criteria, but try explaining that to them.
 

Hershal

Metrologist-Auditor
Trusted Information Resource
Under ILAC and Regional rules, each AB must have procedures to resolve complaints. If you are not getting any action - one way or another - then you may consider lodging and complaint.

You may not agree with the final decision, that is a different question, but you should at least have a definite position.
 
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