Estimating process capability index Cp with various sample types: A practical implementation

C. H. Wu*, W. L. Pearn

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Process precision index Cp has been used widely in the manufacturing industry for measuring process potential and precision. In practice, sample data with various types such as one single random sample, multiple random samples, control chart samples, and samples with gauge measurement errors may be employed to estimate the Cp index for evaluating the process potential capability. If the process is perfectly centered in the specification range, the percentage of process non-conforming (%NC) can be expressed by Cp index. In this paper, a review for estimating and testing of Cp index is presented. Some efficient MATLAB programs and illustrative examples are also provided for each type of sample data.

Original languageEnglish
Pages (from-to)906-916
Number of pages11
JournalJournal of Testing and Evaluation
Issue number4
StatePublished - 1 Jul 2015


  • Critical value
  • Hypothesis testing
  • Lower confidence bound
  • Process capability index
  • Sample types

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