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Topic Diff b/w PPK CPK

Diff b/w PPK CPK

Home Forums Old Forums General Diff b/w PPK CPK

This topic contains 9 replies, has 8 voices, and was last updated by  Bulldog 10 years, 3 months ago.

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  • #128952

    waht exactly is diff b/w PPk & CPk for Sigma Multiple calculation.


    Ppk doesn’t require a process to be in statiscal control, while Cpk does.Ppk can be calculated by using direct calculations of mean and variations from a group of observations, say 40 measurements. Then you use USL, LSL, mean & variation to get Ppk.Cpk is calculated after the Control charts have been constructed and the process is shown in control. And you use the formula of constructing control charts to calculate the mean, variation. Then the Cpk can be calculated.In short, Cpk means a process is in statistical control and its capability as indicated. Ppk not requires in statistical control.Ppk is not useful but creats confusions.




    wow…really wrong…The calculations are identical, with Ppk simply using a long term view of the variation in the process, usually indicating less capability (ie a smaller value than Cpk). 
    It is said to better approximate how your customer experiences the quality of your process.
    A typical capability analysis would run both the C and the P calculations to gain a greater understanding of the current process´s potential – and actual – ability to meet customer specs in both the short and long term.
    Good luck.


    “The calculation are identical, but Ppk usually smaller than Cpk.”


    Is it right to conclude that Cpk explains the ability of the process corresponding to within subgroup variation i.e. a snap shot whereas Ppk indicates ability of the process corresponding to between as well as within  subgroup variation i.e. a long shot? If that is the case Ppk appears to be more meaningful than Cpk.


    Meaningful to talk about capability before a process is in statistically control?


    Add  one  more  thing:Cpk  for  short -term  and  Ppk  for  long-term 


    I  think  it  is  time  that  you  start  to refresh your  knowledge?


    this is about the 3rd time this question has been posted suggest you have a look thourgh the forum …. i would but i can’t be bothered.

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