Reading Preestablished Control Limits

SCHART Statement

Reading Preestablished Control Limits

See SHWSCHR 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 an s chart for new measurements in the data set TURBINE2 (not listed here) using the control limits in TURBLIM:

   title 'Chart for Standard Deviations of Power Output';
    symbol v=dot c=salmon;
   proc shewhart data=turbine2 limits=turblim;
      schart kwatts*day / cframe   = vligb
                          cinfill  = ywh
                          cconnect = salmon;
   run;

The chart is shown in Figure 40.8. The LIMITS= option in the PROC SHEWHART statement specifies the data set containing the control limits. 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 40.8: s Chart for Second Set of Power Output Data

All the standard deviations lie within the control limits, indicating that the variability of 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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