Context-based statistical process control: A monitoring procedure for state-dependent processes

Irad Ben-Gal, Gail Morag, Armin Shmilovici

Research output: Contribution to specialist publicationArticle

50 Scopus citations


Most statistical process control (SPC) methods are not suitable for monitoring nonlinear and state-dependent processes. This article introduces the context-based SPC (CSPC) methodology for state-dependent data generated by a finite-memory source. The key idea of the CSPC is to monitor the statistical attributes of a process by comparing two context trees at any monitoring period of time. The first is a reference tree that represents the "in control" reference behavior of the process; the second is a monitored tree, generated periodically from a sample of sequenced observations, that represents the behavior of the process at that period. The Kullback-Leibler (KL) statistic is used to measure the relative "distance" between these two trees, and an analytic distribution of this statistic is derived. Monitoring the KL statistic indicates whether there has been any significant change in the process that requires intervention. An example of buffer-level monitoring in a production system demonstrates the viability of the new method with respect to conventional methods.

Original languageEnglish
Number of pages19
Specialist publicationTechnometrics
StatePublished - 1 Nov 2003


  • Context tree
  • Kullback-Leibleer statistic
  • Statistical process control

ASJC Scopus subject areas

  • Statistics and Probability
  • Modeling and Simulation
  • Applied Mathematics


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