Computer program for calculating the p-value in testing process capability index Cpmk

W.l. Pearn*, P. C. Lin

*Corresponding author for this work

Research output: Contribution to journalArticle

29 Scopus citations


Many process capability indices, including Cp, Cpk, and Cpm, have been proposed to provide numerical measures on the process potential and performance. Combining the advantages of these indices, Pearn et al. (1992) introduced a new capability index called Cpmk, which has been shown to be a useful capability index for processes with two-sided specification limits. In this paper, we implement the theory of a testing hypothesis using the natural estimator of Cpmk, and provide an efficient Maple computer program to calculate the p-values. We also provide tables of the critical values for some commonly used capability requirements. Based on the test we develop a simple step-by-step procedure for in-plant applications. The practitioners can use the proposed procedure to determine whether their process meets the preset capability requirement, and make reliable decisions.

Original languageEnglish
Pages (from-to)333-342
Number of pages10
JournalQuality and Reliability Engineering International
Issue number4
StatePublished - 1 Jul 2002


  • Critical value
  • p-value
  • Process capability index
  • Testing hypothesis

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