The SHEWHART Procedure |

Overview |

The XCHART statement creates an 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

You have three alternatives for producing charts with the XCHART statement:

Traditional graphics are produced by default.

ODS Graphics output is produced when you specify the ODS GRAPHICS statement prior to the PROC SHEWHART statement.

Legacy line printer charts are produced when you specify the LINEPRINTER option in the PROC SHEWHART statement.

See Chapter 3, SAS/QC Graphics, for more information about producing these different kinds of graphs.

**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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