Westgard rule 22s states that:
- If two consecutive control measurements exceed the same mean by +2 SD or by -2 SD ( or, within a run, if two consecutive control values are outside the same 2 SD) the run must be rejected.
- If this circumstance occurs, a systematic error is likely.
- The top chart represents the day's "normal" control, while the bottom chart shows the day's "elevated" control.
- The L-J plots on the 13th day for both the normal and elevated controls show greater than +2SD. Troubleshooting must be performed before testing can continue.
- Had only one of the controls been greater than +2SD, the run would have been accepted as "in control," but would have been rejected on the next QC run if the same control was again out +2SD.
