<p>From the article, about selection bias</p>
<p>“Most of the students who live in gender-specific housing did not request to be there; they were placed there by the university.” Note the “most,” not “all.” It doesn’t say whether or not they discounted those who had. </p>
<p>And while we will have to wait for the full study to be sure, I also find it hard to believe that students had NO control over what dorm they were in. For instance, at my school, you can chose “Freshmen Only” or “Mixed Class” housing for your freshmen year. The only single sexed halls are in the mixed housing and, surprise surprise, people who chose the all freshmen housing tend to be more inclined to party. So even if people in single-sex halls didn’t chose those specifically, they did chose NOT to be in the freshmen dorms. At other schools, specific dorms are known more to be party dorms, etc.</p>
<p>So unless there is absolutely NO choice about what dorm to be in, I have a hard time believing that there isn’t some selection bias. And, as people have pointed out, this i a really small sample size.</p>