I had several phone interviews, two coding challenges including a written report on the problem and how I tackled it, which I finally had to present to them. The interview was very fun and challenging. I loved it because it is entirely skill based: I am a chemist, but they didn't care, as long as I knew statistics and could program. The questions were very technical and so was their feedback on some things I had done during the challenges, but it was really helpful to understand better the problems and to learn something.