Chances of admittance if I got an invitation to interview?

[KayD]

I am thrilled to say I got an invitation to interview weekend at Duke for the Civil and Environmental Engineering PhD program! I know that different schools have different approaches to interviews, with some schools making interviews competitive with only 25% admission, others where you are basically guaranteed as long as you aren't super awkward or get really drunk, or in the middle inviting 12 and accepting 6. Does anyone have knowledge of where Duke's CEE program stands on the spectrum? 

[Flaco12]

I do not know specifically for CEE, but for ECE an interview is pretty much an admission.  I was admitted to Duke's PhD ECE in fall 2015 and that's what my group members told me.