Defining the Decision Interval for a One-Sided Cusum Scheme
The height of the decision interval is h, expressed as a
multiple of the standard error of the subgroup mean. You can
specify h with the H= option in the XCHART statement
or with the variable _H_ in a LIMITS= data set. The decision
interval is displayed as a horizontal line on the cusum chart,
as illustrated in Figure 12.12.
Figure 12.12: Decision Interval
Interpreting One-Sided Cusum Charts
A shift or
out-of-control condition is signaled at time t if
the cusum St plotted at time t exceeds the decision interval line.
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