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if Cpk is 0.68, what will be the rejection in ppm?

Six Sigma – iSixSigma Forums Old Forums General if Cpk is 0.68, what will be the rejection in ppm?

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  • #47190

    Mohsin
    Participant

    For a process we find out the CPk is 0.68. Can we calculate the rejection in ppm from this figure??
    what is difference between Ppk and Cpk?
    Please help!!

    0
    #157065

    Mikel
    Member

    Rejection in PPM is somewhere between 20,000 and 40,000 (depends where the process is centered)
    Difference between Cpk and Ppk – go read the defintions on this site or go to page 81 of the AIAG SPC manual.

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    #157075

    sonic
    Member

    The difference between cpk and ppk is simple.  Ppk uses sigma while cpk uses sigma hat, or in other words, ppk is your overall process capability while cpk is the capability within your data.  Normally these numbers will be very close.  However, if you want to create “drama” between the two numbers, take sub-group data.  If you have a large discrepency between your subgroups, your cpk and ppk may produce astounding results since cpk uses range to calculate sigma hat.  Using Minitab is the easiest and best way to view information and graphical data.  Minitab will give you both cpk and ppk and allow you to manipulate data to see

    0
    #157078

    Fake Gary Alert
    Participant

    Your process  is  not  capable.
    Cpk  for  short -term,Ppk of  long-term 

    0
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