Create a query into this table.
Depress the Totals button on the toolbar (Upper Sigma icon).
Access adds a Total row to the grid.
One of the choices in this row is Average.
Note that when Access calculates the average for a field, it skips any
records where the field is null. For example, if you have 4 records
containing:
2
4
Null
6
the answer is 4 (12/3), not 3 (12/4).