Implementation of evaluating process capability index C pk for processes with multiple characteristics

W.l. Pearn, Chia-Huang Wu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Process yield has been the most common criterion used in the manufacturing industry for measuring process performance. In many industrial applications, processes often have multiple characteristics with various specifications. The generated yield index C pk T establishes the relationship between the manufacturing specifications and the actual process performance, which provides a lower bound on process yield. In this paper, the explicated formula of the lower confidence bound is derived, and then the lower confidence bound for various values of a-risk, capability requirements, and sample sizes are calculated via the use of R programs. The lower confidence bound is essential to product reliability assurance and is important in the hypothesis testing of process capability. We not only provide some reliable lower confidence bound tables but also develop a simple and practical procedure for engineers. The practitioners can use the proposed procedure to determine whether their process meets the preset capability requirement and to make reliable decisions.

Original languageEnglish
JournalJournal of Testing and Evaluation
Issue number4
StatePublished - 1 Jul 2012


  • Capability index
  • Lower confidence bound
  • Production yield

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