How do you measure impact when you can't run a clean A/B test (difference-in-differences, synthetic control, IV)?
Senior DS loops test causal reasoning beyond the randomized A/B test. What interviewers reward is naming the quasi-experimental method that fits and stating the single assumption it lives or dies on. Here is the answer for when randomization is off the table.
Updated Sep 2026 · Grounded in real GenAI, LLM, and AI/ML engineering interview loops and written to a senior-engineer editorial bar.
Senior DS loops test causal reasoning beyond the randomized A/B test. What interviewers reward is naming the quasi-experimental method that fits and stating the single assumption it lives or dies on. Here is the answer for when randomization is off the table.
Lead with where the obvious approach breaks, because that is the judgment they are screening for — most candidates jump straight to the happy path and lose the room.
Then walk the failure back through the pipeline in order, naming the one metric the customer's exec sponsor actually cares about before you propose the fix.
