Note: See Requesting Tests for Special Causes in the SAS/QC Sample Library.
The data set Assembly
includes a variable named System
, which indicates the manufacturing system used to produce each assembly. As shown by the following statements, this variable
can be temporarily renamed and read as the variable _PHASE_
to create a control chart that displays the phases (groups of consecutive subgroups) for which System
is equal to 'T', 'R', and 'Q':
ods graphics on; title 'Manufacturing Systems Used in Assembly'; proc shewhart history=Assembly (rename=(System=_phase_)); xrchart Offset * Sample / mu0 = 20 sigma0 = 2.24 limitn = 5 alln tests = 1 to 4 testlabel = ( comment ) readphases = ('T' 'R' 'Q') phaselegend phaseref vaxis = 16 to 26 by 2 split = '/' markers; label OffsetX = 'Avg Offset in cm/Range'; run;
The chart is shown in Figure 17.183.
Note that a single set of fixed 3 limits is displayed for all three phases because LIMITN=5 and ALLN are specified. Consequently, the tests requested with the TESTS= option are applied independently of the phases. In general, however, it is possible to display distinct sets of control limits for different phases, and in such situations, the tests are not applied independently of phases, as discussed in the next example.