Alternatively, you can also force normal distribution by clicking "Process Capability" from the red triangle.
Define USL. JMP will show you the Cpk.
![WebDesignesCrow_0-1701653957118.png WebDesignesCrow_0-1701653957118.png](https://community.jmp.com/t5/image/serverpage/image-id/59254iBB6768E9471B9BFA/image-size/medium?v=v2&px=400)
I think only normal distribution will display Cpk.
Cpk = min (Cpu, Cpl).
So, if you have only upper spec limit, Cpk = Cpu because Cpl not exist.
For Non normal distribution (including log normal fitting), JMP will display Ppk.
I prefer to use Ppk because i think it is a better metric compared to Cpk.