Forty-one percent of Tulane’s undergraduate women have been sexually assaulted since arriving on campus, the university reported last month. That’s a shocking statistic, but is it true? The number is worth breaking down because Congress may soon require all colleges to use similar surveys to inform their practices.

One problem is how broadly Tulane defines sexual assault. The school goes beyond rape or attempted rape to include any form of unwanted sexual contact, including a stolen kiss or hug. The latter may be unwelcome...