XCHART Statement

Overview

The XCHART statement creates an $\bar{X}$ chart for subgroup means, which is used to analyze the central tendency of a process.

You can use options in the XCHART statement to

compute control limits from the data based on a multiple of the standard error of the plotted means or as probability limits
tabulate subgroup sample sizes, subgroup means, control limits, and other information
save control limits in an output data set
save subgroup sample sizes and subgroup means 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 chart more readable
display vertical and horizontal reference lines
control axis values and labels
control layout and appearance of the chart

Note: When working with variables data, you should analyze the variability of the process as well as its central tendency. You can use the XRCHART statement or the XSCHART statement in the SHEWHART procedure for this purpose.

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