Resources

In 1924, Walter A. Shewhart introduced the control chart, a pivotal tool in quality improvement that remains essential a century later. Statistical Process Control (SPC) charts, or Shewhart charts, track process variations over time, distinguishing between inherent (common-cause) and unusual (special-cause) variations. These help organisations to answer two key improvement questions: “1) How do our processes vary over time? and 2) Are our processes under current operating conditions capable of meeting the needs of those we serve?”

This differentiation enables organisations to identify when a process is stable or requires intervention. Understanding variation is crucial; all systems exhibit it, and understanding it guides appropriate actions for variance reduction.  Stable processes producing undesirable outcomes necessitate systemic changes, while special-cause variations call for investigation into their sources.