A Comparison of Decision Methods for C pk When Data are Autocorrelated

Peder Lundkvist, Kerstin Vannman, Murat Kulahci

    Research output: Contribution to journalJournal articleResearchpeer-review


    In many industrial applications, autocorrelated data are becoming increasingly common due to, for example, on-line data collection systems with high-frequency sampling. Therefore, the basic assumption of independent observations for process capability analysis is not valid. The purpose of this article is to compare decision methods using the process capability index C-pk when data are autocorrelated. This is done through a case study followed by a simulation study. In the simulation study the actual significance level and power of the decision methods are investigated. The outcome of the article is that two methods appeared to be better than the others.
    Original languageEnglish
    JournalQuality Engineering
    Issue number4
    Pages (from-to)460-472
    Publication statusPublished - 2012


    • Autocorrelation
    • Cpk capability index
    • Continuous process
    • Process industry


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