Learning to Use the SHEWHART Procedure

Introduction

Learning to Use the SHEWHART Procedure

Although the SHEWHART procedure provides a large number of options, you can use the procedure to create a basic Shewhart chart with as few as two SAS statements:

the PROC SHEWHART statement, which starts the procedure and specifies the input SAS data set
a chart statement, which specifies the type of Shewhart chart you want to create and the variables in the input data set that you want to analyze

For example, you can use the following statements to create $\bar{X}$ and R charts with $3\sigma$ limits for measurements read from a SAS data set named DRUMS:

   proc shewhart data=drums graphics;
      xrchart flwidth*hour;
   run;

The keyword XRCHART in the chart statement specifies that $\bar{X}$ and R charts are to be created. The following SAS variables are specified in the XRCHART statement:

A SAS variable (FLWDITH), whose values are the process measurements, is specified before the asterisk. This variable is referred to as the process.
A SAS variable (HOUR), whose values classify the measurements into subgroups, is specified after the asterisk. This variable is referred to as a subgroup-variable.

The same form of specification is used with other chart statements to create different types of Shewhart charts. The following table lists the keywords for the 13 chart statements that are available with the SHEWHART procedure:

Table 1: Chart Statements in the SHEWHART Procedure

Keyword	Chart(s) Displayed
BOXCHART	box chart with optional trend chart
CCHART	c chart
IRCHART	individual and moving range charts
MCHART	median chart with optional trend chart
MRCHART	median and R charts
NPCHART	np chart
PCHART	p chart
RCHART	R chart
SCHART	s chart
UCHART	u chart
XCHART	$\bar{X}$ chart with optional trend chart
XRCHART	$\bar{X}$ and R charts
XSCHART	$\bar{X}$ and s charts

If you are using the SHEWHART procedure for the first time, you should

read Chapter 31, "PROC SHEWHART and General Statements"
read the "Getting Started" section in the chapter for the chart statement you need to create your chart.

Once you have learned to use a particular chart statement, you will find it straightforward to use the remaining chart statements since their syntax is nearly the same. A separate, self-contained chapter is provided for each chart statement.

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