Saving Summary Statistics

See CUSTWOS1 in the SAS/QC Sample LibraryIn this example, the CUSUM procedure is used to save summary statistics and cusums in an output data set. The summary statistics can subsequently be analyzed by the CUSUM procedure (as in the preceding example). The following statements read the raw measurements from the data set `Oil` (see Creating a V-Mask Cusum Chart from Raw Data) and create a summary data set named `Oilhist`:

```title 'Cusum Chart for Average Weights of Cans';
proc cusum data=Oil;
xchart Weight*Hour /
nochart
outhistory = Oilhist
mu0        = 8.100        /* Target mean for process  */
sigma0     = 0.050        /* Known standard deviation */
delta      = 1            /* Shift to be detected     */
alpha      = 0.10         /* Type I error probability */
vaxis      = -5 to 3 ;
label Weight = 'Cumulative Sum';
run;
```

The OUTHISTORY= option names the SAS data set containing the summary information, and the NOCHART option suppresses the display of the charts (since the purpose here is simply to create an output data set). Figure 6.5 lists the data set `Oilhist`.

Figure 6.5: Listing of the Data Set `Oilhist`

 Cusum Chart for Average Weights of Cans

Obs Hour WeightX WeightS WeightC WeightN
1 1 8.0938 0.0596 -.2500 4
2 2 8.0925 0.0902 -.5500 4
3 3 8.1010 0.0763 -.5100 4
4 4 8.1198 0.0256 0.2800 4
5 5 8.1013 0.0265 0.3300 4
6 6 8.0800 0.0756 -.4700 4
7 7 8.1145 0.0372 0.1100 4
8 8 8.0830 0.0593 -.5700 4
9 9 8.0618 0.0057 -2.100 4
10 10 8.1023 0.0465 -2.010 4
11 11 8.1065 0.0405 -1.750 4
12 12 8.0993 0.0561 -1.780 4

There are five variables in the data set.

• `Hour` contains the subgroup index

• `WeightX` contains the subgroup means

• `WeightS` contains the subgroup standard deviations

• `WeightC` contains the cumulative sums

• `WeightN` contains the subgroup sample sizes

Note that the variables in the OUTHISTORY= data set are named by adding the suffix characters X, S, N, and C to the process `Weight` specified in the XCHART statement. In other words, the variable naming convention for OUTHISTORY= data sets is the same as for HISTORY= data sets.

For more information, see OUTHISTORY= Data Set.