I made it to the second day of three interviews. First interview: phone interview. Second: skills test on the computer. Third: onsite.
First interview was easy, just basic questions about why you are interested in working there. The skills test on the second interview was ridiculously challenging. You are given a lot of hard statistical work, data organization work, and data interpretation work that you have to complete in a short period of time. I consider myself an expert in all of the techniques that were assessed and intelligent, but the amount of time needed to complete the tasks was not even close to enough time. If you are given this test, make sure you sufficiently prepare. I think it is hard to pass this test, as I did reasonably well (I thought) but never heard back after taking it.