If you are interested in a free Lean Six Sigma certification (the "White Belt") head on over to www.sixsigmasociety.org/ ... Process capability evaluates the ability of a process to meet customer specifications (CTQs) without additional efforts. It used on many Lean Six Sigma projects. Measures of capability include the Cp, Pp, Cpk, and Ppk. The Cp and Pp measures process potential. The Cpk and Ppk measure the current capability of our process.