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NPCHART Statement 
See SHWNP1 in the SAS/QC Sample Library 
An electronics company manufactures circuits in batches of 500 and uses an np chart to monitor the number of failing circuits. Thirty batches are examined, and the failures in each batch are counted. The following statements create a SAS data set named CIRCUITS,^{*} which contains the failure counts:
data circuits; input batch fail @@; datalines; 1 5 2 6 3 11 4 6 5 4 6 9 7 17 8 10 9 12 10 9 11 8 12 7 13 7 14 15 15 8 16 18 17 12 18 16 19 4 20 7 21 17 22 12 23 8 24 7 25 15 26 6 27 8 28 12 29 7 30 9 ;
A listing of CIRCUITS is shown in Figure 37.1.

There is a single observation for each batch. The variable BATCH identifies the subgroup sample and is referred to as the subgroupvariable. The variable FAIL contains the number of nonconforming items in each subgroup sample and is referred to as the process variable (or process for short).
The following statements create the np chart shown in Figure 37.2:
title 'np Chart for the Number of Failing Circuits'; symbol v=dot c=yellow; proc shewhart data=circuits; npchart fail*batch / subgroupn = 500 cframe = vibg cinfill = vlibg coutfill = salmon cconnect = yellow; run;
This example illustrates the basic form of the NPCHART statement. After the keyword NPCHART, you specify the process to analyze (in this case, FAIL), followed by an asterisk and the subgroupvariable (BATCH).
The input data set is specified with the DATA= option in the
PROC SHEWHART statement.
The SUBGROUPN= option specifies the number of items in each subgroup
sample and is required with a DATA= input data set.
The SUBGROUPN= option
specifies one of the following:
Options such as SUBGROUPN= are specified after the slash (/) in the NPCHART statement. A complete list of options is presented in the "Syntax" section.
Each point on the np chart represents the number of nonconforming items for a particular subgroup. For instance, the value plotted for the first batch is 5.
Since all the points fall within the control limits, it can be concluded that the process is in statistical control.
By default, the control limits shown are 3limits estimated from the data; the formulas for the limits are given
on
"Control Limits" .
You can also read control limits from an input data set; see
"Reading Preestablished Control Limits" .
For computational details, see
"Constructing Charts for Number Nonconforming (np Charts)" .
For more details on reading raw data, see
"DATA= Data Set" .
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