Multiple total rows for tables

Well, averages and standard deviations aren't "totals" per se, so you cannot have total rows for these.

Assuming the table is not just a data range, but a true Excel 2007+ table:

Insert new rows for average and standard deviation below the totals row, leaving at least one empty row in between.

For either measure, reference the table in the formula so that the formula adjusts automatically for added/deleted data.

=AVERAGE(TABLE1[MyTableColumn])

Where "MyTableColumn" is the header for whichever column values you want to average.
If you have given the table a name, replace Table1 with the actual name of the table.