Ryan, 

http://www.asqstatdiv.org/documents/newsletters/Winter%201999.pdf

Try this but what you want is on page 16. It is very interesting document
that is well written. Actually the whole newsletter is interesting. 

Kat

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ryan Grant
Sent: Wednesday, March 28, 2007 10:39 AM
To: [log in to unmask]
Subject: [TN] Explanation of Cpk (Ppk)

Hi all,

I have a supplier that is wondering why we rejected a shipment for
finding a critical dimension as having a Cpk of 0.65 (Ok, technically,
we are calculating Ppk).  None of the 45 measurements were actually out
of spec (although one measurement just missed exceeding the upper limit
by 0.002mm).  Now they want to know why we are rejecting for low Cpk.
Sigh...  

Rather than go through the tedium of carefully explaining what a
distribution is, what it means, how to calculate it and what the
calculation implies, etc., does anyone know of some websites I can point
them to that can explain this?

Any help is appreciated.

Thanks,
Ryan Grant

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