Evaluating the Measurement Process – Part 2

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Thanks so much for reading our publication. We hope you find it informative and useful. Happy charting and may the data always support your position.


Dr. Bill McNeese
BPI Consulting, LLC

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Measurement Systems Analysis/Gage R&R

Comments (5)

  • DuyMay 10, 2019 Reply

    Hi Bill,Thank you so much for your sharing. This is very helpful. I'just wonder that in GRR analysis we compare GRR value with process specification to see if it is significant different, but in Bias we just compare measured value with reference value by hypothesis test, not with specification. In some cases, the bias is large (hypothesis fail) but the process specification is too high so can we still accept the bias of measurement system ?Regards, Duy

    • billMay 10, 2019 Reply

      The bias test is designed to tell if you have bias present.  You can chose not to worry about it if you want ti due to the specifications.  So, you are looking at two different things with the two methodologies.

      • DuyMay 10, 2019 Reply

        Thank for your quick reply and your information. For example, the bias of two measurement system is 0.15 (fail hypothesis test) but the product specification is 2. % contribution of bias/specification is <10% (7.5%) so I decide to not worry about it.  I'm not sure about my justification method because it is not related to any standard but in manufacturing partical we use it alot. The hypothesis test is very easy to fail and we can not adjust the system day to day due to cost and lead time (especially the product tolerance is high like example above). Could you share me the better way to deal with situation ? 

  • KimFebruary 26, 2021 Reply

    Dear Bill. My name is Junho Kim. I am working as a software engineer. I have question while using Gage R&R in MSA analysis of SPC for Excel. We are only interested in the %Tolerance value and NDC value However, we want to study with only one Operator The %Tolerance value and NDC value were not found in the EMP analysis Please tell me how to get %Tolerance value and NDC value in One Operator’s condition I’m looking forward your reply soon. Thank you.

    • billFebruary 27, 2021 Reply

      A gage R&R analysis has more than one operator – only way to determine the impact of different operators.  You can do it with one  operator (Consistency Study) but that will not give you NDC or % tolerance.  But you can use the equations to determine those two values.

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