Chapter Contents
Chapter Contents
Previous
Previous
Next
Next
XSCHART Statement

Output Data Sets

OUTLIMITS= Data Set

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

Table 44.23: OUTLIMITS= Data Set
Variable Description
_ALPHA_probability (\alpha) 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
_LCLS_lower control limit for subgroup standard deviation
_LCLX_lower control limit for subgroup mean
_LIMITN_nominal sample size associated with the control limits
_LSL_lower specification limit
_MEAN_process mean (\overline{\overline{X}} or \mu_{0})
_S_value of central line on s chart
_SIGMAS_multiple (k) of standard error of \bar{X}_{i} or si
_STDDEV_process standard deviation (\hat{\sigma} or \sigma_{0})
_SUBGRP_subgroup-variable specified in the XSCHART statement
_TARGET_target value
_TYPE_type (estimate or standard value) of _MEAN_ and _STDDEV_
_UCLS_upper control limit for subgroup standard deviation
_UCLX_upper control limit for subgroup mean
_USL_upper specification limit
_VAR_process specified in the XSCHART statement

Notes:

  1. If the control limits vary with subgroup sample size, the special missing value V is assigned to the variables _LIMITN_, _LCLX_, _UCLX_, _LCLS_, _S_, and _UCLS_.
  2. If the limits are defined in terms of a multiple k of the standard errors of \bar{X}_{i} and si, the value of _ALPHA_ is computed as \alpha=2(1-\Phi(k)), where \Phi(\cdot) is the standard normal distribution function.
  3. If the limits are probability limits, the value of _SIGMAS_ is computed as k=\Phi^{-1}(1-\alpha/2), where \Phi^{-1} is the inverse standard normal distribution function.
  4. 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.
  5. Optional BY variables are saved in the OUTLIMITS= data set.


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

OUTHISTORY= Data Set

The OUTHISTORY= data set saves subgroup summary statistics. The following variables are saved:


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.

Subgroup summary variables are created for each process specified in the XSCHART statement. For example, consider the following statements:

   proc shewhart data=steel;
      xschart (width diameter)*lot / outhistory=summary;
   run;

The data set SUMMARY contains variables named LOT, WIDTHX, WIDTHS, WIDTHN, DIAMTERX, DIAMTERS, and DIAMTERN. Additionally, the following variables, if specified, are included:

For an example of an OUTHISTORY= data set, see "Saving Summary Statistics" .

OUTTABLE= Data Set

The OUTTABLE= data set saves subgroup summary statistics, control limits, and related information. The following variables are saved:

Variable Description
_ALPHA_probability (\alpha) of exceeding control limits
_EXLIM_control limit exceeded on \bar{X} chart
_EXLIMS_control limit exceeded on s chart
_LCLS_lower control limit for standard deviation
_LCLX_lower control limit for mean
_LIMITN_nominal sample size associated with the control limits
_MEAN_process mean
_S_average standard deviation
_SIGMAS_multiple (k) of the standard error associated with control limits
subgroupvalues of the subgroup variable
_SUBN_subgroup sample size
_SUBS_subgroup standard deviation
_SUBX_subgroup mean
_TESTS_tests for special causes signaled on \bar{X} chart
_TESTS2_tests for special causes signaled on s chart
_UCLS_upper control limit for standard deviation
_UCLX_upper control limit for mean
_VAR_process specified in the XSCHART statement

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


Notes:

  1. 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).
  2. 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.
  3. The variable _TESTS2_ is saved if you specify the TESTS2= option.
  4. The variables _VAR_, _EXLIM_, _EXLIMS_, _TESTS_, and _TESTS2_ 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" .

Chapter Contents
Chapter Contents
Previous
Previous
Next
Next
Top
Top

Copyright © 1999 by SAS Institute Inc., Cary, NC, USA. All rights reserved.