If you're going with a probabilistic argument, I think BYU students are more likely to stick with mormonism (let alone Christianity) than Bryn Mawr students with their gender.

That doesn't mean you aren't stereotyping people, though.

Irrespective of the AI discussion (computers don't care if you're stereotyping or not), I really don't think it's stereotyping to assume someone who went to a school which literally only admits women is probably a woman. There's a difference between assuming someone's gender because they're a cheerleader, and assuming because they won the women's cheerleading championship. I also assume that the person who drives a fire truck is a fire fighter.