If I understand you correctly, your report should be displaying at a grouping footer the subtotal, number of responses, and the average for those (calculated as subtotal/responses) and you want the same kind of display for the entire report.
The first thing to remember is that to get a proper average you must compute the total and the count of the number of all responses, and then the average is the total/count. You can't "average the averages".
Access gets really funny when computing subtotals and totals. Let's assume your report shows each response in the detail, then the subtotals for a group of responses in a group footer, then the grand totals for all responses.
I would set up in VBA code some variables for the subtotals for responses and number of responses and for the totals and the count of responses. Set them to 0 at the beginning of your report (OnOpen). The real trick is to do the computation of these variables using the OnPrint property (of the Details section and the Group footer and header). (If you do the computation in the OnFormat property, Access very nicely double counts most of the values.)
In the Details section, do something like this:
SubtotalResponse = SubtotalResponse + me.response
SubtotalNumber = SubtotalNumber + 1
TotalResponse = TotalResponse me.response
TotalCount = TotalCount + 1
Since each detail is one response, you can just increment the SubtotalNumber by 1 each time in the detail. For safety, you should probably use the Nz() function, which replaces nulls with the value 0 so the addition doesn't fail.
Then, in the GroupHeader (which you can make a height of 0 if you want) do the following:
SubTotalResponse = 0
SubTotalNumber = 0
In the GroupFooter, set the controls as follows:
me.SubTotalResponse = SubTotalResponse
me.SubTotalNumber = SubTotalNumber
me.SubTotalAverage = SubTotalResponse/SubTotalNumber
