Always dress up. You dont have to go in there wearing a suit but definitely go in wearing your best professional looking clothing, dress in office attire with a good shirt and pants. I'm thinking like a white turtleneck shirt and gray pants *just as an example. Nordstrom is a good company to work for. Group interviews consist of them asking each of you questions, I always have a hard time trying not to steal the other persons answer to the same question so I dont sound like a parrot. I hate group interviews.