A wald test for comparing multiple capability indices

Norma F. Hubele, Abdelaziz Berrado, Esma Gel

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


The capability index CPU is recommended for quality features with a unilateral specification of USL. Linearity, flatness, circularity and cylindricity are examples of such quality features. Here, a Wald statistic is developed for testing the equality of k CPU indices. Industrial data sets are used in illustrations. The procedure is extended for testing the equality of k CPL indices, where the index CPL is used to summarize process performance relative to a single lower specification limit.

Original languageEnglish (US)
Pages (from-to)304-307
Number of pages4
JournalJournal of Quality Technology
Issue number4
StatePublished - Oct 2005


  • Capability Analysis
  • Flatness
  • Form Tolerance
  • One-Sided Specifications

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality
  • Strategy and Management
  • Management Science and Operations Research
  • Industrial and Manufacturing Engineering


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