Importance of Interview?

Hi guys. I am applying RD to WashU this winter, and I had a question about the process. How important is the interview in the admissions process at WashU? Is it essential to gain admission? How often do they grant interviews to RD applicants? My plan is to apply to the University on December 16, if I am rejected from my early decision school. If I apply by then, will I likely be given an interview? Do I need to pre-register for an interview, or will they contact me? If they offer me an interview, and I decline, is that by virtue an automatic rejection if I don’t have a really strong reason to decline? Basically, can someone tell me everything they know about interviews at WashU? Thanks in advance.

From the WashU website, “Regular Decision applicants must submit the Common Application by December 4 in order to be matched for an APAP interview. Once you submit your application, you may be contacted for an APAP interview if they are offered in your location.”

Good to know! Thanks.