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XCHART Statement |
Variable | Description |
_ALPHA_ | probability () of Type 1 error |
_ARLIN_ | average run length for zero shift |
_ARLOUT_ | average run length for shift of |
_BETA_ | probability () of Type 2 error |
_DELTA_ | shift () to be detected |
_H_ | decision interval h for one-sided scheme; distance h between origin and upper arm V-mask for two-sided scheme |
_HSTART_ | headstart value |
_INDEX_ | optional identifier for cusum parameters (if the OUTINDEX= option is specified) |
_K_ | reference value k for one-sided scheme; slope of lower V-mask arm for two-sided scheme |
_LIMITN_ | nominal sample size for cusum scheme |
_MEAN_ | estimated process mean () |
_MU0_ | target mean |
_ORIGIN_ | origin of V-mask |
_SCHEME_ | type of scheme (ONESIDED or TWOSIDED) |
_SIGMAS_ | |
_STDDEV_ | estimated or known standard deviation ( or ) |
_SUBGRP_ | subgroup-variable specified in XCHART statement |
_TYPE_ | type (ESTIMATE or STANDARD) of _STDDEV_ |
_VAR_ | process specified in XCHART statement |
Notes:
The OUTLIMITS= data set contains one observation for each process specified in the XCHART statement. For an example, see "Saving Cusum Scheme Parameters" .
Given a process that is eight characters long, the procedure first shortens the prefix to its first four characters and its last three characters and then adds the suffix. For example, the procedure shortens the process DIAMETER to DIAMTER before adding the suffixes.
Variables containing subgroup summary statistics are created for each process specified in the XCHART statement. For example, consider the following statements:
proc cusum data=steel limits=stparm; xchart (width diameter)*lot / outhistory=summary; run;
The data set SUMMARY would contain nine variables named LOT, WIDTHX, WIDTHS, WIDTHN, WIDTHC, DIAMTERX, DIAMTERS, DIAMTERN, and DIAMTERC.
Additionally, if specified, the following variables are included:
For an example creating an OUTHISTORY= data set, see "Saving Summary Statistics" .
Variable | Description |
_CUSUM_ | cumulative sum |
_EXLIM_ | decision interval or V-mask arm exceeded |
_H_ | decision interval |
_MASKL_ | lower arm of V-mask |
_MASKU_ | upper arm of V-mask |
subgroup | values of the subgroup variable |
_SUBN_ | subgroup sample size |
_SUBX_ | subgroup mean |
_SUBS_ | subgroup standard deviation |
_VAR_ | process specified in XCHART statement |
In addition, the following variables are saved if specified:
Note that the variables _VAR_ and _EXLIM_ are character variables of length eight. The variable _PHASE_ is a character variable of length 16.
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