iSixSigma

WHere can I locate a CPK calculator

Six Sigma – iSixSigma Forums Old Forums General WHere can I locate a CPK calculator

Viewing 7 posts - 1 through 7 (of 7 total)
  • Author
    Posts
  • #38465

    Denzil
    Participant

    If 1.33 means 6 parts defective for every 100,000 produced. If I have a cpk of 1.0 on my anaylsis, what will my defects per 100,000 produced?
    Thanks in advance for your help
    Denzil Oliver

    0
    #115062

    Mikel
    Member

    Dude, its called a normal table but here’s some help –

    Cpk
    PPM  if centered
    Cpk 
    PPM if not centered

    1
    2700
    1
    1350

    1.1
    967
    1.1
    483

    1.2
    318
    1.2
    159

    1.3
    96
    1.3
    48

    1.33
    66
    1.33
    33

    1.4
    27
    1.4
    13

    1.5
    7
    1.5
    3

    1.6
    2
    1.6
    1

    1.67
    0.5
    1.67
    0.3

    1.7
    0.3
    1.7
    0.2

    1.8
    0.07
    1.8
    0.03

    1.9
    0.01
    1.9
    0.01

    2
    0.002
    2
    0.001

    0
    #115064

    Tim F
    Member

    Dude II,Of course, you can only use a normal table if the data is normal to begin with! But I expect Stan knew that ;-)Normality is a common assumption, but by no means necessary. With non-normal data (which is not that rare), then you can only make very broad estimates of the defect rate. A process with a calculated Cpk of 1 or 2 could produce (virtually) no defects, or it could produce many more than listed in the previous table.Cpk is a pretty good summary of the capability, but working backwards to predict actual defects is shaky.Tim F

    0
    #115065

    Mikel
    Member

    Let’s see Tim – the guy doesn’t know about the normal table and his numbers for Cpk are wrong but seem to assume the distribution is centered – and you want to tell him to worry about non-normal data.
    How about walking before running? Or did you warn your kids about the dangers of running on icey surfaces when they were crawling?

    0
    #115083

    Denzil
    Participant

    Thanks for your help, This will be a great tool for us
     

    0
    #115102

    Aquinas
    Member
    #115113

    Kumar
    Participant

    You can see a Cpk Calculator at  http://www.sigmaguru.com/9cpcalculator.htm

    0
Viewing 7 posts - 1 through 7 (of 7 total)

The forum ‘General’ is closed to new topics and replies.