The OUTLIMITS= data set saves control limits and control limit parameters. The following variables can be saved:
Variable |
Description |
---|---|
_ALPHA_ |
probability () of exceeding limits |
_INDEX_ |
optional identifier for the control limits specified with the OUTINDEX= option |
_LCLU_ |
lower control limit for number of nonconformities per unit |
_LIMITN_ |
sample size associated with the control limits |
_SIGMAS_ |
multiple () of standard error of |
_SUBGRP_ |
subgroup-variable specified in the UCHART statement |
_TYPE_ |
type (estimate or standard value) of _U_ |
_U_ |
value of central line of chart ( or ) |
_UCLU_ |
upper control limit for number of nonconformities per unit |
_VAR_ |
process specified in the UCHART statement |
Notes:
If the control limits vary with subgroup sample size, the special missing value 'V' is assigned to the variables _LCLU_, _UCLU_, and _LIMITN_.
If the limits are defined in terms of a multiple of the standard error of , the value of _ALPHA_ is computed as , provided that is a constant. Otherwise, _ALPHA_ is assigned the special missing value 'V'.
If the limits are probability limits, the value of _SIGMAS_ is computed as , provided that is a constant. Otherwise, _SIGMAS_ is assigned the special missing value V.
Optional BY variables are saved in the OUTLIMITS= data set.
The OUTLIMITS= data set contains one observation for each process specified in the UCHART statement. For an example, see Saving Control Limits.
The OUTHISTORY= data set saves subgroup summary statistics. The following variables are saved:
the subgroup-variable
a subgroup number of nonconformities per unit variable named by process suffixed with U
a subgroup sample size variable named by process suffixed with N
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.
Subgroup summary variables are created for each process specified in the UCHART statement. For example, consider the following statements:
proc shewhart data=Fabric; uchart (Flaws nDefects)*lot / outhistory=Summary subgroupn = 10; run;
The data set Summary contains the variables Lot, FlawsU, FlawsN, nDefectsU, and nDefectsN.
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 Nonconformities per Unit. Note that an OUTHISTORY= data set created with the UCHART statement can be used as a HISTORY= data set by either the CCHART statement or the UCHART statement.
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 chart |
_LCLU_ |
lower control limit for number of nonconformities per unit |
_LIMITN_ |
nominal sample size associated with the control limits |
_SIGMAS_ |
multiple (k) of the standard error associated with the control limits |
subgroup |
values of the subgroup variable |
_SUBU_ |
subgroup number of nonconformities per unit |
_SUBN_ |
subgroup sample size |
_TESTS_ |
tests for special causes signaled on chart |
_U_ |
average number of nonconformities per unit |
_UCLU_ |
upper control limit for number of nonconformities per unit |
_VAR_ |
process specified in the UCHART 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= option, respectively, or with the corresponding variables in a LIMITS= data set).
The variable _TESTS_ is saved if you specify the TESTS= option. The th character of a value of _TESTS_ is if Test is positive at that subgroup. For example, if you request the first four tests (the ones appropriate for charts) and Tests 2 and 4 are positive for a given subgroup, the value of _TESTS_ has a 2 for the second character, a 4 for the fourth character, and blanks for the other six characters.
The variables _EXLIM_ 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.