Display Value for Missing Statistics

If a statistic cannot be computed, the default display value is a period (.), which is the symbol used to indicate the system-missing value. This is different from an "empty" cell, and therefore the display value for missing statistics is controlled separately from the display value for cells that contain no cases.

1. Open the table builder (Analyze menu, Tables, Custom Tables).
2. Drag and drop Hours per day watching TV from the variable list to the top of the Columns area on the canvas, above How get paid last week.

   Since Hours per day watching TV is a scale variable, it automatically becomes the statistics source variable and the summary statistic changes to the mean.

3. Right-click Hours per day watching TV in the table preview in the canvas pane and select Summary Statistics from the pop-up context menu.
4. Select Valid N in the Statistics list and click the arrow key to add it to the Display list.
5. Click Apply to Selection.
6. Click the Options tab.
7. In the text field for Statistics that Cannot be Computed, type NA.
8. Click OK to create the table.

The text NA is displayed for the mean in three cells in the table. In each case, the corresponding Valid N value explains why: There are no cases with which to compute the mean.

You may, however, notice what appears to be a slight discrepancy—one of those three Valid N values is displayed as a 0, rather than the label None that is supposed to be displayed in cells with no cases. This is because although there are no valid cases to use to compute the mean, the category isn't really empty. If you go back to the original table with just the two categorical variables, you will see that there are, in fact, three cases in this crosstabulated category. There are no valid cases, however, because all three have missing values for the scale variable Hours per day watching TV.