A
Here are clarification for clearing confusion about Cpk
1) Most physical manufacturing processes are normally distributed about the mean. This is irrespective of the specifications needed by the user. Hence in dealing with cases of non symmetrical specifications, process mean has to be mean value of tolerance band of specification. With this approach, you minimize % of tail portion of distribution going out of specifications.
2) Cpk is a ratio of
Numerator-How much mean is away from target
Denominator- How much is the spread
Unfortunately when numerator is zero, denominator doesnot matter. In such cases, increase resolution or decimal accuracy of your equipment to avoid non zero numerator.
3) Cpk is a variable data like loss function. Any variable data can be converted to attribute data. Unfortunately many people convert and interpret Cpk that way. There is no practical physical difference between Cpk of 1.31 and Cpk of 1.35. However people call it as " Fail" or "Pass"
1) Most physical manufacturing processes are normally distributed about the mean. This is irrespective of the specifications needed by the user. Hence in dealing with cases of non symmetrical specifications, process mean has to be mean value of tolerance band of specification. With this approach, you minimize % of tail portion of distribution going out of specifications.
2) Cpk is a ratio of
Numerator-How much mean is away from target
Denominator- How much is the spread
Unfortunately when numerator is zero, denominator doesnot matter. In such cases, increase resolution or decimal accuracy of your equipment to avoid non zero numerator.
3) Cpk is a variable data like loss function. Any variable data can be converted to attribute data. Unfortunately many people convert and interpret Cpk that way. There is no practical physical difference between Cpk of 1.31 and Cpk of 1.35. However people call it as " Fail" or "Pass"