I went through a few steps.
1st was a recruiter call, which was completely normal. Recruiter was great.
2nd was a really simple case study with expected values and probability over the phone.
3rd was a basic case study on camera with diagrams. Had to do with measuring transit users on a subway. Nothing too tough there.
The final round was a collection of interviews with various tech and product people, I think with three. One of them was the boss of the boss I would have had, and he did a case study interview with me as well. The other two were more cultural and product knowledge. The product one was probably the toughest, but that's because I had a lot less experience thinking about those things. Definitely go in prepared to talk about measuring customer success with applications.
I ended up declining and taking an offer with less pay. The only reason was because I was really skeptical about the specific product I was working on and how it might contribute to gambling addiction. Unfortunately, I didn't get a sense of the product side I'd be working on until the last round. My advice to DK would be to try to frontload that more and make sure the recruiters are better prepared to speak to what you'd be working on.