I'm curious about this too. All the sections, except fighter, seem to be calculated in the same manner as Shawk pointed out above. I always try to note the top fighter squad stat breakdown in our monthly squad newsletter. I don't mention any squad names but it's nice to see what kinda of numbers it takes. Often the squad with the best overall Fighter rank clearly doesn't have the best rankings for the separate fighter sections. I've even seen fighter rankings change months after the camp ended and those who were ranked "too high" get knocked down.
I've been hesitant to post about this for fear of it looking like a witch-hunt against another squad - there is enough unpleasant behaviour already on the boards.
So in fear of opening a can of worms, can someone share how this is calculated?