I applied through college or university. The process took 1 week. I interviewed at UCLA (Los Angeles, CA) in Jan 2018
Interview
The interview process is highly dependent on the Professor that you are applying to work for as a graduate level researcher. You could have applied from outside the university and have corresponded via email and in-person, or you could have carried over your employment from undergraduate at the same school. If applying from outside the university, then your GPA from your undergraduate Degree and your extracurricular education really matters and is judged according to the Professor.
Interview questions [1]
Question 1
What is your experience with this field of research and why are you interested in pursuing it as your graduate study?