The BOXCHART statement creates an chart for subgroup means
superimposed with box-and-whisker
plots of the measurements in each subgroup.
Throughout this chapter, a chart of this type is referred
to as a box chart.
This chart is recommended for
large subgroup sample sizes (typically greater than ten).
You can also use the BOXCHART statement to create standard
side-by-side box-and-whisker plots (see Example 32.2
and Example 32.3.1).
You can use options in the BOXCHART statement to
- specify control limits for subgroup means or medians
- compute control limits from the data based on a multiple of
the standard error of the means (or medians) or
as probability limits
- tabulate subgroup summary statistics and control limits
- save control limits in an output data set
- save subgroup summary statistics in an output data set
- read preestablished control limits from a data set
- apply tests for special causes (also known as runs tests and
Western Electric rules)
- specify one of several methods for estimating the process
- specify whether subgroup standard deviations or
subgroup ranges are used to estimate the process standard deviation
- specify a known (standard) process mean and standard deviation
for computing control limits
- create a secondary chart that displays a time trend
removed from the data
(see "Displaying Trends in Process Data" )
- specify one of several methods for calculating quantile statistics
- control the style of the box-and-whisker plots
- display distinct sets of control limits for data from
successive time phases
- add block legends and symbol markers to reveal
stratification in process data
- clip extreme points to make the chart more readable
- display vertical and horizontal reference lines
- control axis values and labels
- control layout and appearance of the chart
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.