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View Full Version : Calculation of ndc is 1.41PV/GRR - Origin of this coefficient? Marius Savoie 30th November 2004, 07:16 AM The caculation of the ndc is 1.41PV/GRR This calculation is for a 97% Confidence level Why 1.41. Someone know the origin of this coefficient ? Atul Khandekar 30th November 2004, 08:50 AM The caculation of the ndc is 1.41PV/GRR This calculation is for a 97% Confidence level Why 1.41. Someone know the origin of this coefficient ? Hello Marius, Welcome to the Cove. The formula is based on Wheeler's Discrimination Ratio. (Evaluating the Measurement Process,2nd Ed. - Wheeler & Lyday) . A brief explanaton can be found Here (http://www.minitab.com/support/answers/answer.aspx?ID=720) Edit: I think there may be a slight error in formula in the article I linked. If I remember right, Wheeler's formula has a "-1" term in place of "+1". I'll look up the the EMP book and post later. Marius Savoie 4th December 2004, 02:18 PM Thank a lot for your very quick and good help Marius :agree1: returnonq 17th March 2008, 04:42 PM Hello, Thanks for addressing the details of a complex procedure such as MSA. The origins of ndc, according to Don Wheeler are in the misapplication of the classification ratio, used in the first edition of his book Evaluating the Measurement Process. There is a white paper at his website addressing this and other Gauge R&R misconceptions. It is from a joint ASA/ASQ conference earlier this month. Dr. Wheeler is a fellow of both organizations. The website is spcpress.com Stijloor 17th March 2008, 07:03 PM Hello, Thanks for addressing the details of a complex procedure such as MSA. The origins of ndc, according to Don Wheeler are in the misapplication of the classification ratio, used in the first edition of his book Evaluating the Measurement Process. There is a white paper at his website addressing this and other Gauge R&R misconceptions. It is from a joint ASA/ASQ conference earlier this month. Dr. Wheeler is a fellow of both organizations. The website is spcpress.com Hello returnong, Have you seen this thread? "GR&R (Gage R&R) as Superstitious Tradition (http://elsmar.com/Forums/showthread.php?t=25541)." Great stuff! Stijloor. returnonq 18th March 2008, 09:08 AM I had not seen other threads, as I am brand new to the Cove and forums. So thanks for the link:thanx:. Dr. Wheeler continues to work on the elimination of traditional GRR in favour of Intraclass Correlation. The March 2008 paper is a condensation of his 2006 book EMP III Using Imperfect Data. I have read the book and worked though the examples. Now I send both GRR & ICS studies to customers, with the quote "After step 6, every aspect of the Gauge R&R Study is erroneous, fallacious, naïve, incorrect and to put it quite simply, wrong. ... a hopelessly flawed analysis." EMP III Using Imperfect Data p.231 & 232 I've been receiving positive responses from customers and auditors. |
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