Reading Preestablished Control Limits

XSCHART Statement

Reading Preestablished Control Limits

See SHWXS1 in the SAS/QC Sample Library

In the previous example, the OUTLIMITS= data set TURBLIM saved control limits computed from the measurements in TURBINE. This example shows how these limits can be applied to new data. The following statements create $\bar{X}$ and s charts for new measurements in a data set named TURBINE2 (not listed here) using the control limits in TURBLIM:

   title 'Mean and Standard Deviation Charts for Power Output';
   symbol v=dot c=salmon;
   proc shewhart data=turbine2 limits=turblim;
      xschart kwatts*day / cframe   = lib
                           cinfill  = bwh
                           coutfill = yellow
                           cconnect = salmon;
   run;

The charts are shown in Figure 44.8. The LIMITS= option in the PROC SHEWHART statement specifies the data set containing preestablished control limit information. By default,^* this information is read from the first observation in the LIMITS= data set for which

the value of _VAR_ matches the process name KWATTS
the value of _SUBGRP_ matches the subgroup-variable name DAY

Figure 44.8: $\bar{X}$ and s Charts for Second Set of Power Outputs

The means and standard deviations lie within the control limits, indicating that the heating process is still in statistical control.

In this example, the LIMITS= data set was created in a previous run of the SHEWHART procedure. You can also create a LIMITS= data set with the DATA step. See "LIMITS= Data Set" for details concerning the variables that you must provide.

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