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Saving Summary Statistics

In this example, the BOXCHART statement is used to create a summary data set that can be read later by the SHEWHART procedure (as in the preceding example). The following statements read measurements from the data set TURBINE and create a summary data set named TURBHIST:

   title 'Summary Data Set for Power Output';
   proc shewhart data=turbine;
      boxchart kwatts*day / outhistory = turbhist
                            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 32.2.

Figure 32.6 contains a listing of TURBHIST.

There are nine variables in the data set TURBHIST.

• DAY is the subgroup variable.
• KWATTSL contains the subgroup minimums.
• KWATTS1 contains the first quartiles for each subgroup.
• KWATTSX contains the subgroup means.
• KWATTSM contains the subgroup medians.
• KWATTS3 contains the third quartiles for each subgroup.
• KWATTSH contains the subgroup maximums.
• KWATTSR contains the subgroup ranges.
• KWATTSN contains the subgroup sample sizes.

Note that the summary statistic variables are named by adding the suffix characters L, 1, X, M, 3, H, R, and N to the process KWATTS specified in the BOXCHART statement. In other words, the variable naming convention for OUTHISTORY= data sets is the same as that for HISTORY= data sets.

If you specify the STDDEVIATIONS option, the OUTHISTORY= data set includes a subgroup standard deviation variable, rather than a subgroup range variable, as demonstrated by the following statements:

   title 'Summary Data Set for Power Output';
   proc shewhart data=turbine;
      boxchart kwatts*day / outhistory = turbhst2
                            stddeviations
                            nochart;
   run;

Figure 32.7 contains a listing of TURBHST2. The variable KWATTSS contains the subgroup standard deviations.

The STDDEVIATIONS option is recommended when the subgroup sample sizes are greater than 10, and it is also recommended when you use the NOLIMITS option to create standard side-by-side box-and-whisker plots.

For more information, see "OUTHISTORY= Data Set" .

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