I received a question after my last blog post asking me to clarify the concept of within and between subgroup variation which is used in calculating Cpk, Cp, Cr, Ppk, Pp, Pr and other statistics. Here is an example I used to help explain the differences. Let’s say that every day I run about 30 … Continued

I often get asked SPC application questions such as: Can Ppk be larger than Cpk? Can Cpk be larger than Cp? Do you recommend CPM, Cpk, Ppk or something else? I prefer to answer these process capability questions with simple one-word answers, but that doesn’t usually satisfy the quality zealot’s curiosity. So here’s the long … Continued