Suppose you could ask a bunch of undergraduates one question to gauge something like their inclination to take significant action based on EA principles, AKA "EA potential." What question would you ask? The (possible) action relevance is EA university group strategy (eg which schools have the most total potential or most potential per student), though I'm not actually sure how important this information is (Stanford EA just happens to have the opportunity to survey many undergrads). We want the question to be able to distinguish potential "hardcore EAs" from potential "non-hardcore EAs" to the degree that's possible. Our current question is: "On a scale from 1-10, how much does maximizing positive impact guide your career thinking/planning? 1 = It's not a consideration, 10 = It's the sole deciding factor."
One consideration with your current question - might it be more impactful to move people from a 5 to a 9 on that question, by informing them about the principles of EA, rather than taking someone who's already a 9 to start with? Of course there's still value in pointing the 9 towards good resources, but you might expect them to find those themselves if they already care so much.