Quality Control Procedures, Documentation and Interpretation: Westgard Rules

Westgard Rule 41s (2)

  • The second part of Westgard Rule 41s says that a run must be rejected if control values have fallen on the same side of the mean for six consecutive testing days, regardless of standard deviation.
  • Looking closely at the plots you will observe that there has been a movement of the values from one level of the control chart to another, as though the mean has changed.
  • Both parts of this rule reveal systematic errors and troubleshooting must be done before testing can resume.

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