I don't know the answer to your questions, but I know that this is why you want to track track track from the time that user types a query to the time they make a credit card purchase. You want to track the page, the link, the day, the hour, the everything possible. Anything less is throwing it at the wall.
When someone requests to be served from your server, you should take every piece of data possible from their machine and save it forever to better aid in your efforts.
