iSixSigma

Convert DPMO/Sigma to Cpk

Definition of Convert DPMO/Sigma to Cpk:

Cpk = Z(short-term) which is sigma level / 3

However, if you are starting with DPMO, convert it to a decimal value (divide by 1,000,000), look this decimal value up in a standard normal curve(z table) and find the corresponding z. (Minitab can do this as well.) This is long-term z. To convert to short-term z which is sigma level:

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z(short term) which is sigma level = Z(long term) + 1.5

Then you can plug into the equation above to get Cpk.

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