OpenAI·Data Scientist·Technical Phone Screen
May 2026
Got a case-style question at what seemed like a technical screen for a DS role at OpenAI. The whole thing was one big experiment design problem about a subscription promotion, and it went pretty deep into causal inference, ROI estimation, and stakeholder communication. Felt like a take-home dressed up as a live interview.
- An online subscription product wants to test giving eligible new users their first month free instead of charging upfront. Design a full experiment and analysis plan to estimate the causal impact of this promotion.
- What should the primary decision metric be for this experiment, and why are simpler metrics like signup rate or retention among signups not enough on their own?
- How would you measure both short-term and long-term impact when the free month shifts the timing of revenue and changes who signs up?
- How would you estimate ROI when the first month is free and some downstream revenue data is missing or only partially observed?
- What are the key pitfalls in this kind of experiment, covering things like selection bias, delayed conversion, seasonality, cannibalization, and heterogeneous treatment effects?
- If your dataset is limited or imperfect, what assumptions or sensitivity analyses would you run?
- How would you present your recommendation from this experiment to a non-technical stakeholder?
“This is a monster of a question.” The rest of the author's notes on Data Scientist interview at OpenAI, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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