<p>Another thought:</p>
<p>Maybe they fill the dorms with all of the kids that ranked it as their first choice (if there isn’t enough space, they pick kids randomly), and then go to filling dorms with their second choices, then third choices etc. etc. So maybe if you get put in your 5th choice, you had bad luck and didn’t get into your 1st choice dorm, and then 2-4 were filled up with kids that had it as their first choice dorms.</p>