I saw this video of the Graduate Student Visiting Day organized by the Psychology Department at North Carolina State University. You can see how applicants, current students, and faculty members are dressed. I'm a female in my early 20s, and I plan on wearing a pair of Old Navy's Mid-Rise Pull-On Straight Pants for Women with a neutral (probably black) sweater, neutral (again, probably black) collared cardigan, and black booties. Personally, I don't feel comfortable wearing proper business slacks or a matching suit and I think this would be obvious to everyone else, too. It's not my style, and I'd rather wear an outfit I feel comfortable and confident in rather than one where I'm uncomfortable and not-so-confident. I highly recommend the Old Navy pants I linked because they're incredibly flattering and comfortable while maintaining a professional look. I found Old Navy has lots of nice dresses that fall past the knee, which means no worrying about your dress flying up or hiking up as you walk.