Interview with professor in economics department. Lasted 30 minutes and basic behavioral questions, with some technical ones on econometrics, modeling, etc. I heard back from them within a week and got an offer.
Student Assistant applicants have rated the interview process at Columbia University with 3 out of 5 (where 5 is the highest level of difficulty) and assessed their interview experience as 100% positive. To compare, the company-average is 69.8% positive. This is according to Glassdoor user ratings.
Here are the most commonly searched roles for interview reports -