Bootstrap confidence interval of the difference between two process capability indices

J. P. Chen*, Lee-Ing Tong

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The process capability index, Cpk, is extensively used to assess process performance in manufacturing industry. Statistical hypothesis testing or an interval estimation of a single Cpk had been derived under a normally distributed process. However, the difference between two process capability indices, Cpk1 - Cpk2, cannot be inferred statistically because of the complexity of the sampling probability theory. This study proposes a bootstrap resampling simulation method to construct the biased corrected percentile bootstrap (BCPB) confidence interval of (Cpk1 - Cpk2), which can be used to select the better of two suppliers. The various simulation results indicate that the bootstrap confidence interval of (Cpk1 - Cpk2) can be employed to evaluate effectively the difference between the performance of two suppliers.

Original languageEnglish
Pages (from-to)249-256
Number of pages8
JournalInternational Journal of Advanced Manufacturing Technology
Issue number4
StatePublished - 10 May 2003


  • Bootstrap method
  • Interval estimation
  • Process capability index
  • Sensitivity analysis

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