Are frats/sororities biased in who they invite to parties/events?

[blahness]

I noticed that on college campuses, fraternities and sororities hand out flyers to parties or events to people who are supposedly attractive or people who look "cool." A lot of people walk by but they only give it to some people. The frat guys especially like it to give them to attractive girls. At least that's what I'm getting from it. Is that true that they select certain people or do they really give it to random people?