How do Cpk and Sigma relate to ppm defective, and how do I justify a Cpk?
Where I work, we generally perform DOEs to verify that a machine is capable before we release it to manufacture saleable product. Generally the DOE studies require that we meet a certain Cpk or Sigma-quality level for each run. So I analyze the resulting data by fitting a curve, and JMP outputs a Cpk and predicted PPM defective. I use the Cpk to justify that the study results are acceptable. I ...