Talk:Process capability index: Difference between revisions

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== Table for sigma levels ==

Either this table, or the table in the wikipedia article with the following link is wrong:

http://en.wikipedia.org/wiki/Six_Sigma#Sigma_levels

I am not an expert, so please someone revise it.

--[[Special:Contributions/59.66.122.148|59.66.122.148]] ([[User talk:59.66.122.148|talk]]) 13:08, 9 January 2014 (UTC)

:No, they're correct. For process capability to be valid, the process must be stable, so yields of Φ(sigma level) - Φ(-sigma level) as given in the table (in the article coupled with this talk page) are correct. As the [[Six Sigma]] article indicates, the yields presented there represent the worst case deterioration of 1.5σ before a [[control chart]] is expected to catch the shift or drift, so yields of Φ(sigma level - 1.5) - Φ(-sigma level - 1.5) (for a shift or drift upward; a shift or drift downward is equivalent—you can do the math) are correct in that article. No action required. -- [[User:DanielPenfield|DanielPenfield]] ([[User talk:DanielPenfield|talk]]) 10:02, 27 January 2014 (UTC)

Example shown has a std. deviation that seems to not match chart data. Mu hat estimate (98.94) is correct, but estimated chart data std. deviation is ~0.869 (unbiased) or ~0.842 (std. population deviation), not 1.03, as stated.

..unless I am missing something or a different method is used for this? Any comments/clarification very welcomed and appreciated.

[[Special:Contributions/165.225.34.90|165.225.34.90]] ([[User talk:165.225.34.90|talk]]) 23:09, 5 November 2016 (UTC)

== Confusing ==

The definitions of Cp, Cpk here are exactly the same as for Pp, Ppk in the article [[Process performance index]]. Are they meant to be the same and just used under different conditions (under statistical control, not under statistical control)? Or are they meant to be different? A statement about this is required. <!-- Template:Unsigned IP --><small class="autosigned">—&nbsp;Preceding [[Wikipedia:Signatures|unsigned]] comment added by [[Special:Contributions/217.13.68.110|217.13.68.110]] ([[User talk:217.13.68.110#top|talk]]) 06:55, 18 July 2017 (UTC)</small> <!--Autosigned by SineBot-->