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
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
- display specification limits on the component
- 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.