UCHART Statement: ANOM Procedure

Saving Decision Limits

See ANMULIM in the SAS/QC Sample LibraryYou can save the decision limits for an ANOM u chart in a SAS data set.

The following statements read the data set MSAdmits (see Creating ANOM Charts for Rates from Group Counts) and save the decision limits displayed in Figure 4.18 in a data set named MSLimits:

proc anom data=MSAdmits;
   uchart Count*ID / groupn    = KMemberYrs
                     outlimits = MSLimits
                     nochart;
run;

The GROUPN= option specifies the number of opportunity units for each group. The OUTLIMITS= option names the data set containing the decision limits, and the NOCHART option suppresses the display of the chart. The data set MSLimits is listed in Figure 4.19.

Figure 4.19: Data Set MSLimits Containing Decision Limits

Decision Limits for Medical/Surgical Admissions Rates

_VAR_ _GROUP_ _TYPE_ _LIMITN_ _ALPHA_ _LDLU_ _U_ _UDLU_ _LIMITK_
Count ID ESTIMATE V 0.05 V 33.0789 V 29


The data set MSLimits contains one observation with the limits for response Count. The variables _LDLU_ and _UDLU_ contain the lower and upper decision limits, and the variable _U_ contains the central line. The value of _LIMITN_ is the nominal number of units associated with the decision limits (which are varying in this case), the value of _LIMITK_ is the number of groups, and the value of _ALPHA_ is the significance level of the decision limits. The variables _VAR_ and _GROUP_ are bookkeeping variables that save the response and group-variable. The variable _TYPE_ is a bookkeeping variable that indicates whether the value of _U_ is an estimate or standard (known) value. Typically, the value of _TYPE_ is 'ESTIMATE.' For more information, see OUTLIMITS= Data Set.

Alternatively, you can use the OUTTABLE= option to create an output data set that saves both the decision limits and the group statistics, as illustrated by the following statements:

proc anom data=MSAdmits;
   uchart Count*ID / groupn   = KMemberYrs
                     outtable = MSTable
                     nochart;
run;

The a partial listing of the data set MSTable is shown in Figure 4.20.

Figure 4.20: Data Set MSTable

Rates and Decision Limits for Medical/Surgical Admissions

_VAR_ ID _ALPHA_ _LIMITN_ _SUBN_ _LDLU_ _SUBU_ _U_ _UDLU_ _EXLIM_
Count 1A 0.05 58.1003 58.1003 31.2135 32.3922 33.0789 34.9443  
Count 1B 0.05 12.8933 12.8933 28.2837 33.9710 33.0789 37.8741  
Count 1C 0.05 2.6633 2.6633 22.1550 37.5481 33.0789 44.0028  
Count 1D 0.05 6.8545 6.8545 26.3640 46.3929 33.0789 39.7938 UPPER
Count 1E 0.05 4.2691 4.2691 24.4964 40.0554 33.0789 41.6615  
Count 1F 0.05 0.2020 0.2020 0.0000 34.6535 33.0789 73.0631  
Count 1G 0.05 0.8626 0.8626 13.7710 32.4606 33.0789 52.3868  
Count 1H 0.05 2.3985 2.3985 21.5579 46.6959 33.0789 44.5999 UPPER
Count 1I 0.05 0.5034 0.5034 7.7757 49.6607 33.0789 58.3822  
Count 1J 0.05 1.5918 1.5918 18.8992 33.9249 33.0789 47.2587  


This data set contains one observation for each group. The variables _SUBU_ and _SUBN_ contain the rate of occurrence and the number of opportunity units for each group. The variables _LDLU_ and _UDLU_ contain the lower and upper decision limits, and the variable _U_ contains the central line. The variables _VAR_ and ID contain the response name and values of the group-variable, respectively. For more information, see OUTTABLE= Data Set.

See ANMUTAB in the SAS/QC Sample LibraryAn OUTTABLE= data set can be read later as a TABLE= data set by the ANOM procedure. For example, the following statements read MSTable and display a u chart (not shown here) identical to the chart in Figure 4.18:

title 'Analysis of Medical/Surgical Admissions';
proc anom table=MSTable;
   uchart Count*id ;
   label _subu_ = 'Admits per 1000 Member Years';
run;

Because the ANOM procedure simply displays the information in a TABLE= data set, you can use TABLE= data sets to create specialized ANOM charts. For more information, see the section TABLE= Data Set.