they're not interviewing for waitlist spots. definitely go, and you have a good chance of getting in based on stats.
plus, the fact that they invited you means they like you.
Also, since you're asking this question, it sounds like you already have acceptances/other interviews/other schools that you'd rather go to.
They get a lot of applicants, and they have a pretty big class size so i'd say you'd have a chance of getting in if you go to the interview.