İHSAN KAYA
CENGIZ KAHRAMAN
ABBAS PARCHAMI
MASHAALLAH MASHINCHI

Process capability indices (PCIs) which are very useful statistical values to summarize process’ dispersion and location can be used for measuring product quality and process performance. Although they have usability in a wide range, these indices have some limitations because of crisp definition of parameters which prevents a deep and flexible analysis Fuzzy set theory can be used effectively to add more information and flexibility to PCIs. In this paper the main parameters of PCIs which are specification limits (SLs), process mean and process variance are defined by using fuzzy set theory. The fuzzy formulations of the most used and most known two PCIs, p C , and pk C are developed.

Process capability indices, fuzzy set theory, mean, variance, specification limits