The SHEWHART Procedure

Note: See Requesting Tests for Special Causes in the SAS/QC Sample Library.

If a test is signaled at a particular point, the point is labeled by default with the index of the test, as illustrated in Figure 17.180.^[44] You can use the TESTLABEL= option to specify a variable in the input data set whose values provide the labels, as illustrated by the following statements:

ods graphics on;
title 'Analysis of Assembly Data';
proc shewhart history=Assembly;
   xrchart Offset * Sample / mu0       = 20
                             sigma0    = 2.24
                             limitn    = 5
                             alln
                             tests     = 1 to 4
                             testlabel = ( comment )
                             vaxis     = 16 to 24 by 2
                             split      = '/'
                             markers;
   label OffsetX = 'Avg Offset in cm/Range';
run;

The labels are shown in Figure 17.183. It is often helpful to specify a variable with the TESTLABEL= option that provides operator comments or other information that can aid in the identification of special causes.