Well, in my research lab, my supervisor and some of us see clinical research participants in jeans and a nice shirt, but I think its well understood that in a professional clinical service environment, more upscale attire is necessary.
What I really meant was make sure your shirt is pressed, your clothes fit, don't have your bare chest showing if your top button is unbottoned (wear and undershirt). For ladies, dont wear stripper heels, fancy jewelry, dangling earrings, etc. Although, its important to note I have seen the opposite of this as well. We used to have a girl in our program who grew up in a commune in the mountains. At our in-house clinic, she used to wear what I could only decribe as a "hippie skirt" (it was probably made of wheat or something) and she reaked of patchuli stank. I found it embarrassing. Patchuli? Really?? What are you, 16? You are a professional, grow-up and wear a big girl perfume...😉