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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.