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Westgard Rule R4s

The R4s rule applies to controls within a run. If two controls exceed 4SD, that is, if one control exceeds +2SD and the other control (or another control, if more than 2 controls are tested) exceeds -2SD, the run should be rejected. This is the case on day 13, as seen on the normal and abnormal L-J QC charts on the right.