Is it possible to come up with a CPK for a part with a single control limit. We take readings on the part and the minimum reading allowed (the single control limit) is 25, however it can be above 25, just not below 25. Therefore we have readings anywhere from 25 to 55. How would I go about calculating a CPK with the single Control Limit of 25? I'm sure this is very simple for most everyone, but I'm very new to the Quality Assurance program. Any help would be greatly appreciated. Thank you all.