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Capability and Performance Indices

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The following links are to a 'sister' website to this site, and address common questions about the use and validity of Process Performance and Process Capability Indices.

Process Stability and Cpk

  • When studying a process, is a stable process a prerequisite for Cpk? 
  • The information on this page explains why the calculation and reporting of Cpk is valid only when the process is shown to be stable (statistically in-control).

Process Stability and SPC Charts

  • When studying a process, are SPC charts necessary to demonstrate that a process is stable? 

Process Validation and Process Stability

  • For a process to be considered "validated", is it a prerequisite to show that the process is stable (statistically in-control)?

Process Verification and Statistical Sampling

  • Are we required to use a statistical sampling system during process verification and for determining conformance of product when manufacturing  lots/batches?

Process "Worst Case" (aka "Challenge") Conditions and DOE

  • Is the use of DOE required to determine “worst case” conditions?

Statistical Methods and Regulatory Compliance (in the Medical Device Industry)

  • Do medical device industry regulations and standards really require the use of appropriate statistical methods?