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  Measurement, Test and Calibration
  Duncan's Tables

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Author Topic:   Duncan's Tables
Atul Khandekar
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Posts: 21
From:Pune, India
Registered: Mar 2000

posted 02 October 2000 10:48 AM     Click Here to See the Profile for Atul Khandekar   Click Here to Email Atul Khandekar     Edit/Delete Message   Reply w/Quote
QS9000 MSA manual referes to "Duncan's Table D3 for d2* ", to look up the degrees of freedom related to No. of parts, operators and trials. (See : Confidence Interval for Average and Range Gage Study)

Are these tables available for reference anywhere on the web?

Thanx,

-Atul.

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Rick Goodson
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Posts: 102
From:Wuakesha, Wisconsin, USA
Registered: Aug 2000

posted 02 October 2000 11:29 AM     Click Here to See the Profile for Rick Goodson   Click Here to Email Rick Goodson     Edit/Delete Message   Reply w/Quote
Is there a reason you can not used the table on Page 29 in the MSA manual? It is straight from Duncan's book, 'Quality Control and Industrial Statistics'.

d2* is a modification of d2 that gives weight to the number of samples (subgroups) used to compute R-bar. If more than 20 subgroups are used the factor is almost identical to d2.


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Atul Khandekar
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Posts: 21
From:Pune, India
Registered: Mar 2000

posted 03 October 2000 02:59 AM     Click Here to See the Profile for Atul Khandekar   Click Here to Email Atul Khandekar     Edit/Delete Message   Reply w/Quote
I can't use it because it gives only d2* values and not Degrees of Freedom.

I use that table for calculations of R&R though.

-Atul.

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Rick Goodson
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Posts: 102
From:Wuakesha, Wisconsin, USA
Registered: Aug 2000

posted 03 October 2000 02:20 PM     Click Here to See the Profile for Rick Goodson   Click Here to Email Rick Goodson     Edit/Delete Message   Reply w/Quote
The table is also available in Ott's Text, "Process Quality Control" ISBN 0-07-047923-2 as table A-11.

Unless you need 'absolute' accuracy you can etimate df from the formula
df ~ (.9)g(m-1).

ie:

g m table df calc df
6 2 5.5 5.4
10 3 18.4 18.0
15 3 27.5 27.0
10 5 36.5 36.0
20 7 105.7 108.0

Hope that helps.

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