Having an issue with using an average formula in my cross-tabs and line graphs.

My formula to calculate average talk time is {table.talktime} / {table.interactions} where talktime is the total talk time in seconds and interactions is the number of interactions being handled.

The table looks similar to this:

INTERVAL TALKTIME INTERACTIONS

06:00:00 1/1/2011 0 0

07:00:00 1/1/2011 37250 36

08:00:00 1/1/2011 12697 13

09:00:00 1/1/2011 1462 2

Giving me a total talk time of 51,409 seconds across 51 interactions. Therefore, the average is about 1008.02 seconds.

If I drop my formula in the "summarized field" section of the crosstab, my average is displayed as 131.12. If I change the summary to a weighted average with table.interactions it's 759.04. Both are wrong.

However, if I simply drop {table.talktime} into the "summarized field" section with a weighted average with table.interactions, I get closer with 1600.76. But it's still not right. What can I do?

And then line graphs - I don't know how to do this either. Do i need to change my average formula to take in a "group by" value?

My column in table.Interval. I have nothing in the rows - only in the summarized fields and column.