Quality Control Procedures, Documentation and Interpretation: Westgard Rules

Westgard Rule 41s (1)

  • Westgard Rule 41s has two main parts.
  • The first part states that a run is to be rejected if the control values were beyond ±1SD for four consecutive testing days, the control for the fourth day is rejected.
  • In the illustration to the right, you will notice that on the 10th, 11th, and 12th of the month, the control results were greater than ±1SD from the mean. The control was again greater than 1SD on the 13th, resulting in the testing procedure being out of control for the 13th.

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