I would say with your profile, you can probably score about 30-40 points below there average. However anything below that would put you in a weak position. Your profile is stronger than most, but that being said, you also have to concider with USC's average, they probably are accepting individuals with must stronger profiles that choose not to attend USC. So the true average of the accepted individuals are probably in the range of 60-80 points higher than the floor I gave you.
Another thing to consider is that your peer group who have a finance background generally are strong test takers, more so than entertainment, or HR background, which means you still need to be competitive with other finance individuals. I hope this helps.
The average listed GMAT for Marshal is 620.
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