Standby for Candidates Weekend 2015

My kid is on standby for CW. Does anybody have historical knowledge about the stats here? how many kids selected for CW decline the invitation? I assume those with EA to MIT, Stanford or the likes might decline but just want to have an idea to either encourage or not

I was invited but applied ED2 somewhere, If I was accepted at the ED2 school I would have to cancel participation at CW.

Thank you!