The SHEWHART Procedure

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;
   xrchart Flangewidth * 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 (Flangewidth), 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 13 chart statements that are available with the SHEWHART procedure:

Table 18.1: Chart Statements in the SHEWHART Procedure

Statement	Chart(s) Displayed	"Getting Started" Section
BOXCHART	Box chart with optional trend chart	Getting Started: BOXCHART Statement
CCHART	c chart	Getting Started: CCHART Statement
IRCHART	Individual and moving range charts	Getting Started: IRCHART Statement
MCHART	Median chart with optional trend chart	Getting Started: MCHART Statement
MRCHART	Median and R charts	Getting Started: MRCHART Statement
NPCHART	$np$ chart	Getting Started: NPCHART Statement
PCHART	p chart	Getting Started: PCHART Statement
RCHART	R chart	Getting Started: RCHART Statement
SCHART	s chart	Getting Started: SCHART Statement
UCHART	u chart	Getting Started: UCHART Statement
XCHART	$\bar{X}$ chart with optional trend chart	Getting Started: XCHART Statement
XRCHART	$\bar{X}$ and R charts	Getting Started: XRCHART Statement
XSCHART	$\bar{X}$ and s charts	Getting Started: XSCHART Statement

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

Read PROC SHEWHART and General Statements.
Read the "Getting Started" subsection in the section for the chart statement you need to create your chart. Table 18.1 provides links to these sections.

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