Design human review to estimate model accuracy
Company: Google
Role: Data Scientist
Category: Statistics & Math
Difficulty: hard
Interview Round: Onsite
# Design human review to estimate model accuracy
You need to estimate the **accuracy** of an ML classifier on a population of subjects.
You can only afford **K total human reviews**. Each human review produces a **binary judgment** (0/1) for a subject (assume it is intended to represent the “true label,” but reviewers may be noisy).
You must choose how to allocate reviews:
- **Option 1:** review **K different subjects once each** (1 review per subject).
- **Option 2:** review **fewer subjects**, but assign **multiple independent reviews per subject**, and use **majority vote** (or another aggregation).
**Question:** Which option is better for estimating the model’s accuracy, and under what assumptions? Provide a statistical argument, discuss bias/variance trade-offs, and propose a practical review design (including how you would quantify uncertainty with a confidence interval).
### Constraints & Assumptions
- Preserve the scope, facts, inputs, and requested outputs from the prompt above.
- If the prompt leaves a detail unspecified, state a reasonable assumption before relying on it.
- Keep the answer interview-ready: concise enough to present, but concrete enough to implement or evaluate.
### Clarifying Questions to Ask
- Clarify the random variables, distributional assumptions, independence assumptions, and desired output.
- Show enough derivation for the interviewer to follow the reasoning.
- Explain how you would validate the result with simulation or sensitivity checks.
### What a Strong Answer Covers
- A correct setup with definitions, formulas, and boundary conditions.
- A step-by-step derivation or estimation plan.
- Interpretation of the result, including uncertainty and practical limitations.
- Checks for assumptions, edge cases, and numerical stability.
### Follow-up Questions
- How would the result change if the assumptions were relaxed?
- Can you verify the answer with a simulation?
- What is the most likely source of estimation error?
Quick Answer: This interview question evaluates statistical assumptions, formulas, estimation strategy, uncertainty, edge cases, and interpretation in a realistic interview setting. A strong answer for Design human review to estimate model accuracy states assumptions, handles edge cases, explains trade-offs, and shows how to validate the result clearly.