NPCHART Statement: SHEWHART Procedure

Saving Proportions of Nonconforming Items

Note: See np Chart Examples in the SAS/QC Sample Library.

In this example, the NPCHART statement is used to create a data set that can be read later by the SHEWHART procedure (as in the preceding example). The following statements read the number of nonconforming items from the data set Circuits (see Creating np Charts from Count Data) and create a summary data set named Cirhist:

proc shewhart data=Circuits;
   npchart Fail*Batch / subgroupn  = 500
                        outhistory = Cirhist
                        nochart;
run;

The OUTHISTORY= option names the output data set, and the NOCHART option suppresses the display of the chart, which would be identical to the chart in Figure 18.52. Figure 18.55 contains a partial listing of Cirhist.

Figure 18.55: The Data Set Cirhist

Subgroup Proportions of Failing Circuits

Batch	FailP	FailN
1	0.010	500
2	0.012	500
3	0.022	500
4	0.012	500
5	0.008	500

There are three variables in the data set Cirhist.

Batch contains the subgroup index.
FailP contains the subgroup proportion of nonconforming items.
FailN contains the subgroup sample size.

Note that the variables containing the subgroup proportions of nonconforming items and subgroup sample sizes are named by adding the suffix characters P and N to the process Fail specified in the NPCHART statement. In other words, the variable naming convention for OUTHISTORY= data sets is the same as that for HISTORY= data sets.

For more information, see OUTHISTORY= Data Set.