Presumably the 3% is a proportion of the total enrollment for those classes, but you still need some other figure to compare to, like the proportion of basketball players on campus (though certainly much smaller than 3%). I suppose you could also consider the probability of taking those classes is in one group (athletes) vs. other (everyone else).

Of course, what I really want to know, as an educator and Tarheel alumnus, is why the hell are there 54 course with little or no instruction to begin with...hopefully those are just transferred credits from Duke or NCState :)