Talk:Process capability index

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--- I propose to use the example of a runway instead. Everybody can imagen that you would like the pilot to land at the middle of the runway each time. -gr, JVP —Preceding unsigned comment added by 145.36.63.11 (talk) 14:45, 20 January 2011 (UTC)[reply]

I corrected the notation for "variability of the process" to standard deviation to avoid confusion between sigma and sigma squared, variance/variability, and standard deviation. Hyoga 11/26/2007

There is no point in listing an equation if you are not going to define what the variables mean. Namely, what on earth is do USL and LSL stand for? Even sigma should be defined for those who do not know what they are looking at.

Fixed. --mabahj 11:00, 12 July 2006 (UTC)

USP - Upper Specification Limit LSL - Lower specification Limit These are related to statistical process control (SPC). -- Manaf 28 June 2007 (EST)

... and how are these interpreted?

It would be really helpful, I think, if someone could add a sentence or two for each measure to say what a "good" value is ... e.g., 1.0 is good, higher is better, things like that. Sn14534 13:13, 19 July 2007 (UTC)[reply]

C_pk

I have noticed that the Ckp value equation has an mistake; there shoud be T instead of µ (targed instead of estimated/calculated mean). If µ is used, the result is PPk. Could someone make the correction, please.

Antti 29th Aug 2007 —Preceding unsigned comment added by 192.130.237.254 (talk) 06:57, August 29, 2007 (UTC)

C_pk does not take the target, T, into account according to NIST (http://www.itl.nist.gov/div898/handbook/pmc/section1/pmc16.htm) or Montgomery (http://he-cda.wiley.com/WileyCDA/HigherEdTitle/productCd-0471656313.html). Perhaps you're thinking of a variant on C_pk that does? — DanielPenfield 16:24, 5 September 2007 (UTC)[reply]

Is there a missing word in the following clause? 'is', maybe? And is this English? I'd much prefer "Because the process capability..."

Being the process capability a function of the specification

--71.10.226.43 (talk) 12:28, 18 September 2009 (UTC)[reply]

Please see 8-14b on the following link: http://www.math.wsu.edu/math/faculty/lih/10-11s.pdf; regarding your statement about Cpk, you say that, "Estimates what the process is capable of producing if the process target is centered between the specification limits." The word, NOT, should be added before the word centered and the word "target" needs to be replaced with the words estimator of process mean uhat or simply xbar. Cpk is calculated when the process mean is not centered. Do you agree? Jun 30 2011

I've attempted to clarify. -- DanielPenfield (talk) 20:57, 30 June 2011 (UTC)[reply]
I've actually corrected the statement 18 AUG 2011 — Preceding unsigned comment added by 75.215.56.118 (talk) 20:03, 18 August 2011 (UTC)[reply]

Not really--you just reworded it. -- DanielPenfield (talk) 21:33, 18 August 2011 (UTC)[reply]