Six Sigma Calculations - 1.5 Shift vs Non-Shift Calculation

If you look at published information, when you say you're at 6 Sigma quality, then it's 3.4 dppm, this includes a 1.5 Sigma shift. So are you saying ignore this shift? So if your data shows you have 3.4 dppm, then you should say you're at 4.5 Sigma?

My company is going thru APQP and reviewing the Cpk of all our critical dimensions. I need to calculate and present the Cpk. Trying to understand the calculations to determine if I should present the Cpk with a 1.5 Sigma shift or not.

Don’t include the shift. It is stupid meaningless irrelevant untrue etc. just report the straight Cpk value.
Stop talking about a X sigma process that is as old as bloomers

Thank you all the feedback. Just one last question. I'll be capturing about 200 data points, spread across about 4 different batches manufactured on 4 different dates in the span of 1 year. I had thought to include the 1.5 Sigma shift when calculating the Cpk because data is across batches (i.e. long-term). So your recommendation is to never consider this 1.5 Sigma shift regardless of dataset?

I think I recall a country song titled "What Part of No Don't You Understand?".

elnguyen said:

My company is going thru APQP and reviewing the Cpk of all our critical dimensions. I need to calculate and present the Cpk. Trying to understand the calculations to determine if I should present the Cpk with a 1.5 Sigma shift or not.

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The automotive industry has NEVER included the 1.5 sigma shift in Cp/Cpk/Pp/Ppk calculations. Get the AIAG blue books (APQP, SPC, etc.) for reference. Their calculations do not show it.

@elnguyen OK. You’ve been told no many many times. You’ve been told why it is not valid. You have been told that there is no requirement. Are you over it now?

Thank you all for the feedback.

elnguyen said:

Thank you all the feedback. Just one last question. I'll be capturing about 200 data points, spread across about 4 different batches manufactured on 4 different dates in the span of 1 year. I had thought to include the 1.5 Sigma shift when calculating the Cpk because data is across batches (i.e. long-term). So your recommendation is to never consider this 1.5 Sigma shift regardless of dataset?

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The effect of batch to batch (aka long term) should also be included. You will need to understand the different formula as for Cpk and Ppk

I think it's just an AI bot trying to test us...