IRCHART Statement: SHEWHART Procedure

Output Data Sets

OUTLIMITS= Data Set

The OUTLIMITS= data set saves control limits and control limit parameters. The following variables can be saved:

Table 15.21 OUTLIMITS= Data Set
Variable	Description
_ALPHA_	probability ( $\text{[math]}$ ) of exceeding limits
_CP_	capability index $\text{[math]}$
_CPK_	capability index $\text{[math]}$
_CPL_	capability index $\text{[math]}$
_CPM_	capability index $\text{[math]}$
_CPU_	capability index $\text{[math]}$
_INDEX_	optional identifier for the control limits specified with the OUTINDEX= option
_LCLI_	lower control limit for individual measurements
_LCLR_	lower control limit for moving ranges
_LIMITN_	number of consecutive measurements used to compute moving ranges
_LSL_	lower specification limit
_MEAN_	process mean
_R_	value of central line on moving range chart
_SIGMAS_	multiple ( $\text{[math]}$ ) of standard error of individual measurement or moving range
_STDDEV_	process standard deviation ( $\text{[math]}$ or $\text{[math]}$ )
_SUBGRP_	subgroup-variable specified in the IRCHART statement
_TARGET_	target value
_TYPE_	type (estimate or standard value) of _MEAN_ and _STDDEV_
_UCLI_	upper control limit for individual measurements
_UCLR_	upper control limit for moving ranges range
_USL_	upper specification limit
_VAR_	process specified in the IRCHART statement

Notes:

If the limits are defined in terms of a multiple $\text{[math]}$ of the standard errors of $\text{[math]}$ and $\text{[math]}$ , the value of _ALPHA_ is computed as $\text{[math]}$ , where $\text{[math]}$ is the standard normal distribution function.
If the limits are probability limits, the value of _SIGMAS_ is computed as $\text{[math]}$ , where $\text{[math]}$ is the inverse standard normal distribution function.
The variables _CP_, _CPK_, _CPL_, _CPU_, _LSL_, and _USL_ are included only if you provide specification limits with the LSL= and USL= options. The variables _CPM_ and _TARGET_ are included if, in addition, you provide a target value with the TARGET= option. See Capability Indices for computational details.
Optional BY variables are saved in the OUTLIMITS= data set.

The OUTLIMITS= data set contains one observation for each process specified in the IRCHART statement. For an example, see Saving Control Limits.

OUTHISTORY= Data Set

The OUTHISTORY= data set saves individual measurements and moving ranges. The following variables are saved:

the subgroup-variable
an individual measurements variable named by process
a moving range variable named by process suffixed with R

Given a process name that contains 32 characters, the procedure first shortens the name to its first 16 characters and its last 15 characters, and then it adds the suffix.

A variable containing the moving ranges is created for each process specified in the IRCHART statement. For example, consider the following statements:

proc shewhart data=Steel;
   irchart (Width Diameter)*Lot / outhistory=Summary;
run;

The data set Summary contains variables named Lot, Width, WidthR, Diameter, and DiameterR.

Additionally, the following variables, if specified, are included:

BY variables
block-variables
symbol-variable
ID variables
_PHASE_ (if the OUTPHASE= option is specified)

For an example of an OUTHISTORY= data set, see Saving Individual Measurements and Moving Ranges.

OUTTABLE= Data Set

The OUTTABLE= data set saves individual measurements, moving ranges, control limits, and related information. The following variables are saved:

Variable	Description
_ALPHA_	probability ( $\text{[math]}$ ) of exceeding control limits
_EXLIM_	control limit exceeded on individual measurements chart
_EXLIMR_	control limit exceeded on moving range chart
_LCLI_	lower control limit for individual measurements
_LCLR_	lower control limit for moving range
_LIMITN_	number of consecutive measurements used to compute moving ranges
_MEAN_	process mean
_R_	average range
_SIGMAS_	multiple (k) of the standard error associated with control limits
subgroup	values of the subgroup variable
_SUBI_	individual measurement
_SUBR_	moving range
_TESTS_	tests for special causes signaled on individual measurements chart
_UCLI_	upper control limit for individual measurements
_UCLR_	upper control limit for moving range
_VAR_	process specified in the IRCHART statement

In addition, the following variables, if specified, are included:

BY variables
block-variables
symbol-variable
ID variables
_PHASE_ (if the READPHASES= option is specified)

Notes:

Either the variable _ALPHA_ or the variable _SIGMAS_ is saved, depending on how the control limits are defined (with the ALPHA= or SIGMAS= options, respectively, or with the corresponding variables in a LIMITS= data set).
The variable _TESTS_ is saved if you specify the TESTS= option. The $\text{[math]}$ th character of a value of _TESTS_ is $\text{[math]}$ if Test $\text{[math]}$ is positive at that subgroup. For example, if you request all eight tests and Tests 2 and 8 are positive for a given subgroup, the value of _TESTS_ has a 2 for the second character, an 8 for the eighth character, and blanks for the other six characters.
The variables _EXLIM_, _EXLIMR_, and _TESTS_ are character variables of length 8. The variable _PHASE_ is a character variable of length 48. The variable _VAR_ is a character variable whose length is no greater than 32. All other variables are numeric.

For an example, see Saving Control Limits.