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    Process Capability (Cp/Cpk) and SPC

    Statistical metrics and methods for monitoring whether a process meets its specifications.

    Reviewed by Christian Espinosa, Founder, Blue Goat CyberLast reviewed May 5, 2026

    Definition

    Statistical Process Control (SPC) uses control charts to monitor process stability. Process capability indices Cp and Cpk quantify how well a stable process fits within specification limits, with Cpk accounting for centering.

    What this means in practice

    Process validation per the FDA/GHTF guidance expects capable and stable processes. Common medical-device targets are Cpk ≥ 1.33 for routine attributes and ≥ 1.67 for safety-critical ones.

    Primary references

    3 sources
    Link health: 3 verified· last checked 2026-05-09
    GHTF·1FDA·1ISO·1
    1. 1
      GHTF Process Validation Guidance
      Verified
      GHTFimdrf.org
    2. 2
      FDA - Device Manufacturing
      Verified
      FDAfda.gov
    3. 3
      ISO 13485 Standard Page
      Verified
      ISOiso.org

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