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Statistical Techniques and 6 Sigma d2 chart value?

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Author  Topic: d2 chart value? 
David Drue Stauffer Forum Contributor Posts: 25 
posted 10 January 2001 11:09 AM
Hi folks, I am trying to determine how the d2 values for subgroup sizes is derived. Does anyone know how this value is derived or where I can go to find out? a book, a web site, another forum, etc.? IP: Logged 
Jim Biz Forum Wizard Posts: 275 
posted 10 January 2001 02:43 PM
You Might Try Juran's Quality Handbook Chapters 21 thru 24 deal with charting and the factors used Also Table A (pg AII3 lists d2 values for samle sizes ranging from 2 to 25) IP: Logged 
Laura M Forum Contributor Posts: 299 
posted 10 January 2001 09:31 PM
Do you mean the actual calculation that was used to generate the values in the table? I remember deriving it a long time ago in a "Theory of Statistics" course. That would certainly stimulate some brain cells if that's what your looking for. Laura IP: Logged 
David Drue Stauffer Forum Contributor Posts: 25 
posted 20 February 2001 04:02 PM
Laura, Yes that's exactly what I mean. You can make some really useful macro charts in excel IF you know how the formula is derived. Example: What range do I need to hold if I have a total tolerance of .030 and a subgroup size of 10, and I need a 1.67 Cp? Since the calculation for Cp is the Tolerance divided by 6 sigma and 1 sigma is Rbar times d2, to put the macro in the spreadsheet, I need to know how d2 is calculated. IP: Logged 
Rick Goodson Forum Wizard Posts: 102 
posted 20 February 2001 04:59 PM
David, I do not remember the formula nor the derivation but it has to do with the distribution of the relative range where w = R/sigma prime for different sample sizes. I do have a reference for you, but it is probably going to be hard to find. I found it in Acheson Duncan's book "Quality Control and Industrial Statistics". The paper is "The Probability Integral of the Range in Samples of N Observations from a Normal Population". It was published in Biometrika, Vol. XXXII (194142) pp 301  8. Good luck finding it. Couldn't you just load the table into the spreadsheet and use the Lookup function to find the value? IP: Logged 
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