As others have said, I think that as long as you are comfortable and in business dress it doesn't really matter.
If you rarely wear a skirt (like me and maybe Scooby) then you might feel very awkward in one on your interview day. With the stress of the interview do you want to be worrying about whether your legs are crossed or whether your hose has run. On the other hand, if you wear skirts and dresses often and you feel more confident in them - go for it.
I have a very formal looking double-breasted navy pants suit. I've had great luck in it with job interviews, and I feel very confident while wearing it.
A few years ago I was looking for a job and I met with an executive recruiter. He actually chastised me at our meeting because I didn't look professional enough. I still remember some of the advice he gave me - wear a watch or people will think that you are too flaky to pay attention to the time, get rid of your backpack and get a nice black folder to put copies of your resume in, don't bring that empty coffee cup into our meeting, you should have thrown it away before you came in here, you should have anticipated some of these questions I am asking you and already had answers (questions like, tell me about your skills, why are you looking for a job in this field, etc.) I thought he was a jerk, and he never did find me anything.
He did help in one way, though. When I'm preparing for an interview, I feel that I have a concrete list of tasks to do - have my suit cleaned, find my watch, print out my resume and put it in my folder, look up information on the company, think of some questions to ask, think of answers to basic questions. I doubt that any interviewer really cares whether or not I have a watch on, but when I walk into an interview, I feel that I have all my t's crossed and i's dotted because I've taken care of all the things on my list. I feel more confident and I think that shows.
This was long winded, but my point is this: I don't think your dress will directly effect your admissions i.e. she wore pants and I hated her yellow blouse - she's outta here. But if you find an outfit that makes you feel like a million bucks (skirt, pants, whatever just professional), you will hold your head higher and speak with more confidence and that may effect your chances on admission.
