There is something inherently wrong with calculating Cpk with only a few measurements--see my earlier post in this thread. Even using the standard rules, Cpk is not a very useful statistic, but if you throw out the rules, the value becomes less than zero.There is nothing inherently wrong with using only a few measurements to calculate a Cpk value
I suspect that anyone who thinks that doing a capability study of 30 pieces is OK is "...not firm in statistics."Personally, I get the impression that you and your customer did not properly specify the expected outcome of the study. Thus, I expect that your customer is not firm in statistics...
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