Expert Data Science Dilemmas

Walk into your next data-science interview having already made every mistake — in the app, not in the room.

More than 900 multiple-choice questions on what data-science, ML and AI-engineering interviews actually test in 2026. Every topic runs from fundamentals to expert scenarios, and the wrong answers are the product: distractors an average-good candidate would pick, so you learn to tell “correct” from “almost correct” — the exact skill interviews measure.

Nine topics, tuned to 2026

• GenAI & LLMs · RAG · Agents & Tooling · Evals
• Classic ML · Statistics · A/B Testing · Causal Inference
• NEW Sampling Design — the data problems S&P 500 companies actually face, and the sampling strategy each one demands: control groups, labeling budgets, streaming data, and the traps in between.

It finds your level — per topic

Each topic carries its own level; questions are drawn to match it. Answer well and it moves you up. Go cold and it eases off, rebuilds, and brings you back. The home screen ranks your topics weakest-first and tells you exactly what would move you up.

Private by design

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