
Tanks Taz, I tried to show why some guys can tink it posible, as I said in the lasts posts, I agree with you in every point of this topic.
Cp or pp CAN NOT BE CALCULATED FOR UNILATERAL, because the Cp, Cpk, pp, ppk take in account that the specs are centered on the target, so, if you calculate it with
cp = (Target - LSL)/(3 Sigma) or cp = (USL - Target)/(3 Sigma)
you implicate that the other spec limit exists, and there is two possible ways:
1- that the tolerance is just from the target to the limit, desto, the other spec limit is on the target (the target not centered on specs, and so violate the consideration that the target is centered on specs).
2- That the other limit is at the same distance from the "official spec", so it's wrong to calculate the cpk/ppk with only the "official spec".
