MCHART Statement: SHEWHART Procedure
| Overview: MCHART Statement |
The MCHART statement creates a chart for subgroup medians, which is used to monitor the central tendency of a process.
You can use options in the MCHART statement to
compute control limits from the data based on a multiple of the standard error of the plotted medians or as probability limits
tabulate subgroup sample sizes, subgroup medians, control limits, and other information
save control limits in an output data set
save subgroup sample sizes and subgroup medians 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 standard deviation
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)
display distinct sets of control limits for data from successive time phases
add block legends and symbol markers to reveal stratification in process data
superimpose stars at points to represent related multivariate factors
clip extreme points to make the charts more readable
display vertical and horizontal reference lines
control axis values and labels
control layout and appearance of the chart
You have three alternatives for producing medians charts with the MCHART statement:
ODS Graphics output is produced if ODS Graphics is enabled, for example by specifying the ODS GRAPHICS ON statement prior to the PROC statement.
Otherwise, traditional graphics are produced by default if SAS/GRAPH® is licensed.
Legacy line printer charts are produced when you specify the LINEPRINTER option in the PROC statement.
See Chapter 3, SAS/QC Graphics, for more information about producing these different kinds of graphs.
Note: When analyzing variables data, you should examine the variability of the process as well as the mean level. You can use the MRCHART statement in the SHEWHART procedure to monitor both the mean level and variability.