Tovia Smith filed a report with NPR that detailed the psychometric delicacies of trying to measure the sexual assault rates on a college campus. I think this story is highly relevant to college students. I also think it also provides an example of the challenge of operationalizing variables as well as self-selection bias. This story describes sexual assault data collected at two different universities, Rutgers and U. Kentucky. The universities used different surveys, had very different participation rates, and had very different findings (20% of Rutgers students met the criteria for sexual assault, while only 5% of Kentucky students did). Why the big differences? 1) At Rutgers, students where paid for their participation and 30% of all students completed the survey. At U. Kentucky, student participation was mandatory and no compensation was given. Sampling techniques were very different, which opens the floor to student discussion about what this might mean for the results. Who m...