Overview
Comparative histograms are useful for comparing the
distribution of a process variable across levels
of classification variables.
You can use the COMPHISTOGRAM statement to create
one-way and two-way comparative histograms.
When used with a single classification variable, the
COMPHISTOGRAM statement displays an array of component
histograms (stacked or side-by-side), one for each
level of the classification variable. When used with
two classification variables, the COMPHISTOGRAM statement
displays a matrix of component histograms, one for each
combination of levels of the classification variables.
In quality improvement applications, typical uses of
comparative histograms include
-
comparing the capability of a process
before and after an improvement
-
comparing process capabilities of two or
more suppliers
-
exploring stratification in process data
due to different lots, machines, manufacturing methods, and so forth
-
studying the evolution of process capability
over successive time periods
You can use options in the COMPHISTOGRAM statement to
- specify the midpoints for histogram intervals
- specify the number of rows and/or columns of
component histograms
- display specification limits on the component
histograms
- display density curves for fitted normal distributions
- display kernel density estimates
- request graphical enhancements
- inset summary statistics and process capability indices
on the component histograms
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.
