XCHART Statement: CUSUM Procedure

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 6.13.

Figure 6.13: Decision Interval

Decision Interval

Interpreting One-Sided Cusum Charts

A shift or out-of-control condition is signaled at time t if the cusum $S_{t}$ plotted at time t exceeds the decision interval line.