Tier system in SWTOR

If you do not win the conversation roll, then since you didn't say it, the companion does not get any affection points.

You have to both choose the appropriate option to gain (or lose) affection with the current companion, and win the roll.

Of course your companion must be summoned and in the group, so this only works for groups less than 4.

It is not like Light/Dark side choices where you get the points for what you chose regardless of who won the roll.

Pre-release the best formula thrown around was roughly described as follows:

If you are ‘naked’ in a bracketed match then you will be up to a 90% combat stats disadvantage. If you are in an open match then the bolster mitigates the difference, not the whole. In other words, you will be at about a ((your level/max level) * 80%) + 10% combat stats disadvantage. Note that formula is an oversimplification for illustrative purposes.

Link for this is here: http://www.swtor-life.com/humor/under-the-hood-the-forumulas-behind-the-mayhem/2268/

I would imagine the actual formula is much more complex to take gear into account, however, practice seems to show that "twinked" 50s gear allows a huge advantage, so, the formula, when it comes to light, is not one for the mind-bending math junkies.