I've also heard that you should dress for exams for the same reason. You feel professional and then you perform better. Frankly, I couldn't imagine wearing a suit for an exam and I can't imagine that the pantyhouse would do a lot for my focus.
I think you should go how you feel least uncomfortable. I don't say most comfortable because that would probably be too casual for most people. If the idea of being one of the few oddballs out of business attire, then wear a suit. If you really dislike suits and feel like you're in frosted mini-wheats commercial, then just wear really conservative business casual attire. Business casual is somewhat amorphous, so I'd say go for tailored pants/trousers and pair it up with a nice button down shirt (like the ones from Gap). Almost anything (except the capri pants) from Ann Taylor count as business casual.
I suppose you can't go wrong with a suit. I don't think that it will help you in any way, but it certainly won't hurt you. If you dress too casual, it might make you appear not serious about the process. But if you dress appropriately causual, then it won't hurt either. One thing I should mention is that the director nor any other person in the administration of the school wore suits, so I certainly don't think suits are the tone they are trying to set for interview day. They dressed conservative, but not business attire. If they wanted to you to wear suits, they would say wear a suit or wear suits themselves. That's how it is at my work. Like I said it won't hurt, but it won't help either.
P.S. how old are you? If you are very young and straight out of college, I won't probably tell you to wear a suit (even if you look like you're in the frost mini wheats comercial), just because it might give you a more serious edge. I'm 26 and I look younger, but I graduated from law school and have been working in top law firms for 2 years now, so I think that fact establishes me as more serious. Anyhow, good luck!
