Cpk for 0 as Ideal Value



I'm trying to figure out if it is possible to calculate Cpk for this type of proces:

Machine sticks label on product, according to spec this label can be shifted to the left or right by max. 1 mm. Ideally there is 0 mm shift.

So I set USL for 1 (shift to the right side) and LSL for -1 (shift to the left side) but I'm not sure if I can use negative numbers for LSL.

Can somebody point me in right direction...

Steve Prevette

Deming Disciple
Super Moderator
Still works, even with negative numbers. If it does cause issues, you could always choose some positive number, say the label is 15 mm from the edge of the product. So, the LSL is 14, target is 15, and USL is 16 . . .
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