when men wear dress shoes, pants, belt, shirt and tie, what is the equivalent on a lady?

i could see a conservative business suit in the category, but what else?

does age make a difference? the age group is 17-26ish. maybe more like 18-23 years old.

occasion? i am supposed to speak(with powerpoint) to a group(maybe 30 or so)

ps it is not a real presentation, but a class assignment.

the male prof says, men wear this, tie, etc, and then doesnt say anything about women, because since hes a man he says he doesnt know. fair enough, but i dont want to be underdressed since its for a grade.

i was thinking dress shoes, suit pants and a button up. all non crazy colors and styles. appropriate enough or not enough?

also if anyone could recommend a book about ladies formal/business attire that i could get at barnes and nobles. com or something, thatd be great too

especially someone in twenties and thirties. i need an idea how it looks like. i have one, but i not sure if it okay. professional looking. business colors. dressing for an interview.