This article describes how to go from a standard crosstab or grid table...
...to a table that displays an Average of all the rows per column:
A table with rows and columns.
1. Select your table.
2. Go to Properties > RULES on the object inspector.
3. To apply the rule, select the Plus (+) > Browse Online Library > Table Computations > Average of Each Column.
4. Select the Statistic to use (if different from the default).
5. Press OK.
This rule adds an extra row to the bottom of the table which shows the Average of the statistics that are shown in the columns. Rows which are duplicates of other rows, for example the NET row, are not included in the computation of the average. Note, this rule can only apply to a single statistic and no significance tests are conducted on these averages.
Note, if you select Switch rows and columns on your table, the rule will no longer work due to the table dimensions changing. In this case, you will have to apply the Average of Each Row rule instead.