Optiver Quantitative Researcher interview questions

I first had to give an online assessment, followed by a call with a trader. Next steps were a call with a recruitment HR, and a quantitative researcher. I failed on the next step, which was a take home assessment which involved performing data analyses on some real world data. In case I would have been selected, the HR informed that me that the next steps would have been an interview with a QR to explain my code, followed by a team compatibility interview with either a head of QR, or a team head. Overall, a great set of interview questions. Slightly salty that I could not make the cut, but honestly, I wouldn't have it any other way -- getting into this company ought to take more effort than I put in, which was basically skimming through the probability section of the green book.

There was a series of assessments, and I could pass through the first one but the second one which is about betting was quite hard. While I was expecting those kina of questions but I couldn't find any proper resources to practice.