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SCHART Statement |
Each observation in a DATA= data set must contain a value
for each process and a value for the subgroup-variable.
If the
i^{ th} subgroup contains n_{i} items, there should be n_{i}
consecutive observations for which the value of the
subgroup-variable
is the index of the i^{ th} subgroup.
For example, if each subgroup
contains five items and there are 30 subgroup samples, the DATA= data
set should contain 150 observations.
Other variables that can
be read from a DATA= data set include
By default, the SHEWHART procedure reads all of the observations in a DATA= data set. However, if the DATA= data set includes the variable _PHASE_, you can read selected groups of observations (referred to as phases) with the READPHASES= option (for an example, see "Displaying Stratification in Phases" ).
For an example of a DATA= data set, see "Creating Standard Deviation Charts from Raw Data" .
proc shewhart data=info limits=conlims; schart weight*batch; run;
The LIMITS= data set can be an OUTLIMITS= data set that was created in a previous run of the SHEWHART procedure. Such data sets always contain the variables required for a LIMITS= data set; see Table 40.22. The LIMITS= data set can also be created directly using a DATA step. When you create a LIMITS= data set, you must provide one of the following:
In addition, note the following:
For an example, see "Reading Preestablished Control Limits" .
A HISTORY= data set used with the SCHART statement
must contain the following:
The names of the subgroup standard deviation and subgroup
sample size variables must be the process name concatenated
with the special suffix characters S and N, respectively.
For example, consider the following statements:
proc shewhart history=summary; schart (weight yldstren)*batch; run;
The data set SUMMARY must include the variables BATCH, WEIGHTS, WEIGHTN, YLDSRENS, and YLDSRENN.
Note that if you specify a process name that contains eight characters, the names of the summary variables must be formed from the first four characters and the last three characters of the process name, suffixed with the appropriate character.
Other variables that can be read from a HISTORY= data set include
By default, the SHEWHART procedure reads all the observations in a HISTORY= data set. However, if the data set includes the variable _PHASE_, you can read selected groups of observations (referred to as phases) by specifying the READPHASES= option (see "Displaying Stratification in Phases" for an example).
For an example of a HISTORY= data set, see "Creating Standard Deviation Charts from Subgroup Summary Data" .
The following table lists the variables required in a TABLE= data set used with the SCHART statement:
Table 40.24: Variables Required in a TABLE= Data SetVariable | Description |
_LCLS_ | lower control limit for standard deviation |
_LIMITN_ | nominal sample size associated with the control limits |
_S_ | average standard deviation |
subgroup-variable | values of the subgroup-variable |
_SUBN_ | subgroup sample size |
_SUBS_ | subgroup standard deviation |
_UCLS_ | upper control limit for standard deviation |
Other variables that can be read from a TABLE= data set include
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