According to Wikipedia:

Estimates vary greatly as to the number of women who experience a sexual assault during college, with surveys focused on the United States placing it as low as 1 in 50 (2%)[1] to as high as 1 in 4 (25%).

It seems to me that if studies get so much variance they are likely to be methodologically flawed, if not outright fraudolent.

Moreover:

Rape prevalence among women in the U.S. (the percentage of women who experienced rape at least once in their lifetime so far) is in the range of 15–20%, with different studies disagreeing with each other. (National Violence against Women survey, 1995, found 17.6% prevalence rate;[7] a 2007 national study for the Department of Justice on rape found 18% prevalence rate.[8])

A 15–20% overall rape prevalence in the general female population seems inconsistent with a ~20% prevalence in the female college population, unless you assume that college women are have an exceptionally high risk of being raped, which I would find surprising (I expect that the majority of rapes occurs to victims from socially degraded and impoverished backgrounds).