Process capability indices were originally invented to enable an organization to make economically sound decisions for process management. Process capability is a comparison of the voice of the process with the voice of the customer. Current practice is to use Cp and Cpk regardless of the validity of the underlying assumptions necessary for their use. Even if all necessary assumptions are satisfied, important problems can be missed if these indices are the sole process evaluation examined. Customer-supplier axioms are introduced to motivate more useful process evaluations and foster long-term harmonious relationships. This paper explores the alternative capability indices Cpm, Cpmk, Cjkp, Cθ, and Cs and loss function approaches including Taguchi's unbounded quadratic loss function and the multivariate upside-down normal loss function. Illustrative case studies are presented.

Meeting Name

Industrial Engineering Research Conference


Engineering Management and Systems Engineering

Second Department

Mathematics and Statistics

Keywords and Phrases

Process Capability; Quadratic Loss Function; Voice of the Customer; Voice of the Process

Document Type

Article - Conference proceedings

Document Version

Final Version

File Type





© 2007 Institute of Industrial Engineers (IIE), All rights reserved.