The EWMACHART statement creates an exponentially weighted moving average (EWMA) control chart, which is used to determine whether a process is in a state of statistical control and to detect shifts in the process average.
You can use options in the EWMACHART statement to
specify the weight assigned to the most recent subgroup mean in the computation of the EWMAs
compute control limits from the data based on a multiple of the standard error of the plotted EWMAs or as probability limits
tabulate the EWMAs, subgroup sample sizes, subgroup means, subgroup standard deviations, control limits, and other information
save control limit parameters in an output data set
save the EWMAs, subgroup sample sizes, subgroup means, and subgroup standard deviations in an output data set
read control limit parameters from an input data set
specify one of several methods for estimating the process standard deviation
specify a known (standard) process mean and standard deviation for computing control limits
display a secondary chart that plots a time trend removed from the data
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 chart 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 EWMA charts with the EWMACHART 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.