Output Data Sets
The OUTLIMITS= data set saves control limits and control
limit parameters. The following variables can be saved:
Table 35.23: OUTLIMITS= Data Set
Variable
|
Description
|
_ALPHA_ | probability ( ) of exceeding limits |
_CP_ | capability index Cp |
_CPK_ | capability index Cpk |
_CPL_ | capability index CPL |
_CPM_ | capability index Cpm |
_CPU_ | capability index CPU |
_INDEX_ | optional identifier for the control limits specified with
the OUTINDEX= option |
_LCLM_ | lower control limit for subgroup median |
_LCLR_ | lower control limit for subgroup range |
_LCLS_ | lower control limit for subgroup standard deviation |
_LIMITN_ | sample size associated with the control limits |
_LSL_ | lower specification limit |
_MEAN_ | value of central line on median chart ( , , , or ) |
_R_ | value of central line on R chart |
_S_ | value of central line on s chart |
_SIGMAS_ | multiple (k) of standard error of Mi |
_STDDEV_ | process standard deviation ( or ) |
_SUBGRP_ | subgroup-variable specified in the MCHART statement |
_TARGET_ | target value |
_TYPE_ | type (estimate or standard value) of _MEAN_ and _STDDEV_ |
_UCLM_ | upper control limit for subgroup median |
_UCLR_ | upper control limit for subgroup range |
_UCLS_ | upper control limit for subgroup standard deviation |
_USL_ | upper specification limit |
_VAR_ | process specified in the MCHART statement |
Notes:
- The variables _LCLS_, _S_, and _UCLS_ are included
if you specify the STDDEVIATIONS option; otherwise,
the variables _LCLR_, _R_, and _UCLR_ are included.
These variables
are not used to create median charts, but they allow the
OUTLIMITS= data set to
be used as a LIMITS= data set with the BOXCHART, XRCHART, XSCHART,
and MRCHART statements.
- If the control limits vary with subgroup sample size, the special
missing value V is assigned to the variables
_LIMITN_, _LCLM_, _UCLM_,
_LCLR_, _R_, _UCLR_, _LCLS_, _S_, and _UCLS_.
- If the limits are defined in terms of a multiple k of
the standard error of Mi,
the value of _ALPHA_ is computed as
, where Fmed(·,n) is the cumulative distribution function of
the median of a random sample of n standard normally
distributed observations, and n is the value of _LIMITN_.
If _LIMITN_ has the special missing value V, this value
is assigned to _ALPHA_.
- If the limits are probability limits, the value of _SIGMAS_
is computed as
, where Fmed-1(·,n)
is the inverse distribution function of the median of a random
sample of n standard normally distributed observations, and n
is the value of _LIMITN_.
If _LIMITN_ has the special missing value V, this value
is assigned to _SIGMAS_.
- 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 MCHART statement.
For an example,
see "Saving Control Limits" .
The OUTHISTORY= option saves subgroup summary statistics.
The following variables can be saved:
- the subgroup-variable
- a subgroup median variable named by process
suffixed with M
- a subgroup range variable named by process
suffixed with R
- a subgroup standard deviation variable named by
process suffixed with S
- a subgroup sample size variable named by
process suffixed with N
A subgroup standard deviation variable is included if you specify
the STDDEVIATIONS option; otherwise, a subgroup range variable
is included.
Given a process name that contains eight characters, the procedure
first shortens the name to its first four characters and its last
three characters, and then it adds the suffix. For example, the
procedure shortens the process DIAMETER to DIAMTER before
adding the suffix.
Variables containing subgroup summary statistics
are created for each process
specified in the MCHART statement.
For example, consider the following statements:
proc shewhart data=steel;
mchart (width diameter)*lot / outhistory=summary;
run;
The data set SUMMARY contains
variables named LOT, WIDTHM, WIDTHR, WIDTHN,
DIAMTERM, DIAMTERR, and DIAMTERN.
The variables WIDTHR and DIAMTERR are included, since the
STDDEVIATIONS option is not specified. If you specified the
STDDEVIATIONS option, the data set SUMMARY would contain WIDTHS and
DIAMTERS rather than WIDTHR and DIAMTERR.
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 Summary Statistics" .
The OUTTABLE= data set saves subgroup summary statistics,
control limits, and related information. The following
variables are saved:
Variable
|
Description
|
_ALPHA_ | probability ( ) of exceeding control limits |
_EXLIM_ | control limit exceeded on median chart |
_LCLM_ | lower control limit for median |
_LIMITN_ | nominal sample size associated with the control limits |
_MEAN_ | estimate of process mean ( , , , or ) |
_SIGMAS_ | multiple (k) of the standard error associated with
control limits |
subgroup | values of the subgroup variable |
_SUBMED_ | subgroup median |
_SUBN_ | subgroup sample size |
_TESTS_ | tests for special causes signaled on median chart |
_UCLM_ | upper control limit for median |
_VAR_ | process specified in the MCHART 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)
- _TREND_ (if the TRENDVAR= 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 k th
character of a value of _TESTS_ is k if Test k
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 _VAR_, _EXLIM_, and _TESTS_
are character variables of length 8.
The variable _PHASE_ is a character variable of length
16. All other variables are numeric.
For an example, see "Saving Control Limits"
.
Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.