Measuring PPM non-conformities for processes with asymmetric tolerances

W.l. Pearn, Chia-Huang Wu*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Process yield has been the most basic and common criterion used in the manufacturing industry for evaluating process capability. The Cpk index has been used widely in the manufacturing industry. In this note, we considered a generalization of Cpk index which handles processes involving a target T with asymmetric tolerances. Particularly, we established a formula for measuring the PPM non-conformities for given ratios of the two-side tolerances. We proved the validity of the established formula and tabulated the upper bounds on PPM non-conformities for various given Cpk index values and ratios of the two-side tolerances.

Original languageEnglish
Pages (from-to)431-435
Number of pages5
JournalQuality and Reliability Engineering International
Issue number3
StatePublished - 1 Apr 2013


  • Asymmetric tolerances
  • non-conformity
  • process yield
  • target

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