CUSUM Example: Calculating CUSUM - LabCE.com, Laboratory Continuing Education

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CUSUM Example: Calculating CUSUM

Now, we'll calculate the CUSUM value for each daily control.
The CUSUM tracks the cumulative distance from the mean, taking into account whether each daily control fell above or below the mean.
On March 2, the daily result equaled the control, so the CUSUM is 0.
On March 3, the daily control was +3 from the mean, so we add +3 to the previous day's CUSUM, for a total of +3.
On March 4, the daily control was -1 from the mean, so we add -1 to +3, resulting in +2.
On March 5 and 6, the CUSUM again changes -1 each day, since each control result is -1 from the mean.