I applied through college or university. I interviewed at Columbia University (New York, NY) in Feb 2020
Interview
Interviewers consisted of three professors and two post-doc fellow. Roughly ten minutes for each person. The whole interview process was smooth, the professors were very kind. But you have to have direct relevant research experience.
Interview questions [1]
Question 1
Research experience, publications, and relevant work experience.
I applied online. I interviewed at Columbia University
Interview
Met with 3 to 4 professors individually along with the other potential classmates. There was also a candidate dinner later in the day. The process was relatively casual. I picked professors that I wanted to interview with but at least two of the professors ended up being assigned.