## Deriving Control Chart Constants

You can use the functions D2, D3, and C4 to calculate standard control
chart constants that are derived from *d*_{2}, *d*_{3} and *c*_{4}. For
reference, the following equations for some of these
constants are provided:

In the preceding equations, *k* is the multiple of standard
error (*k*=3 in the case of 3 limits), and *n* is
the subgroup sample size. The use of these control chart constants is
discussed in the *ASQC Glossary and Tables for Statistical
Quality Control*, the *ASTM Manual on Presentation of Data and Control Chart Analysis*,
Montgomery (1996), and Wadsworth and others (1986).

Although you do not ordinarily need to calculate control chart
constants when using the SHEWHART procedure, you may find the D2, D3,
and C4 functions useful for creating LIMITS= data sets that contain
control limits to be read by the SHEWHART procedure.

Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.