Haven't had yet the interview (this is my first time looking for a job in the US) but can tell you that after they select your Resume, they send you a case for you to solve in app a week. The case I receive was about identifying problems and finding solutions for reducing the therapy drop out rate in an hypothetical situation in a public hospital (diabetes patients). I was very fun but took my a while. I had to do data analysis but was relatively simple (obtain p-values).

ideas42 has an extremely stretched-out hiring timeline, which is disrespectful to applicants. You cannot expect people to wait around for 4 months for a hiring decision. Also, if you're going to waitlist applicants BEFORE interviewing them, at least provide some feedback on the extensive case study required in stage two. What a frustrating and non-transparent process.