Selecting Top rated discussions.  

How does mylot select its top rated discussions of the day? is it through the number of posts that the user selects or by the user's data or by the topic which the user has selected?or is it taken randomly?actually my dad has been in this circuit for over a year now and i've used to sit with him and watch and i've never seen his discussion rated as the top of the days discussion not even for once..wat is the reason behind that? even though he has written nearly 5000 posts i havent seen it even once as the top of the days post..can some one explain me how some posts are gettin lots of response and some are not even gettin even a few? even thought the subjects of both the posts are identical and have been posted within a gap of 1 week?