it cant be stats nor ratings and if they are they have a very small influence. look at my outside players and compare them to the other players. my shooting % are equal or better. and my player ratings are equal or better than the guys that were picked. I am not upset this happened, i just have to make sure they play more to make it into the allstar team, which won´t happen because training for now is much more important...
Stats might be weighed by minutes played in some way, so given equal contribution, a player who plays 30mpg will get more votes than someone who plays 20.
And I don't think shooting percentages are the most important stat: I imagine it might be as little as points, rebounds and assists.
"I don't know half of you half as well as I should like; and I like less than half of you half as well as you deserve."