Pp vs. Cp

Peter,
Your question is “What does the k stand for?” When you calculate the distance the mean is from the closest specification limit, you use a z-score. That is, you calculate the distance of the average from the spec limit in units of the std. dev. (take the distance and divide by 3-sigma).
This calculation used to be referred to as a k-value (1950’s?)(later referred to as z). Hence the confusion. Maybe we should start calling it Cz ??
Eileen Beachell, Quality Disciplines