why haven't i received my acceptance yet?

<p>I applied to the university of pittsburgh in july at one of their tours. My application was then completed by the end of July and I sent in all of my recommendation letters and essay and resume by the beginning of September. I have a 4.0 GPA, an 1150 on my SATs (out of 1600), I am in many extras, and I am 6th in my class out of 315 students. I applied to the school of arts and sciences as undecided, but i have yet to recieve my acceptance letter. My two friends also applied to pitt and already recieved their acceptance letters within this past week. I applied before both of them. I have a better GPA than both of them and my SATs are better than the one. They both were accepted, the only difference is that they applied to a certain major, while i applied to undecided. i'm very concerned as to why i haven't received my acceptance yet, especially since i applied before both of then. Please give me reasons of why this might be and also if i still might have a chance to being accepted.</p>