There is a small percentage of application randomly picked up for interview for quality purposes. Also, applications that did not have enough evidence will also be called for interview (which is in my case when I was a bit overly confident to not submit all the house paperwork we had). We went to the interview and they kicked us out of the office after 5 minutes because this time we brought all of our bills, investment, and house paperwork that were 5 inches thick.
Good luck.