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Meta·Data Scientist·Technical Phone Screen·Senior

Senior
Jun 2026

Summary

Meta DS interview focused entirely on product experimentation for a short-video feed context. Two meaty questions back to back, no warmup, no behavioral fluff. Felt more like a product analytics case than a traditional data science screen.

Questions Asked (2)

Q1

What are the top three metrics you would use to measure user engagement in a short-video feed?

Product Analytics & MetricsA/B Testing & Experimentation
Author's notes

I went with watch time per daily active user, like-to-view ratio, and session frequency.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal of measuring engagement—whether it's to optimize for retention, time spent, or meaningful interactions—and then propose a balanced set of metrics that capture depth, breadth, and quality of engagement. Structure your answer around a framework like 'active engagement, passive consumption, and retention' to show strategic thinking, and tie each metric to a business outcome.

Pro tip: Emphasize that no single metric is perfect and that you'd triangulate multiple metrics to avoid gaming; mention that you'd validate metrics through A/B tests and guardrail metrics to ensure they align with long-term user value.

1. Clarify the objective

Ask whether the goal is to maximize short-term engagement, long-term retention, or user satisfaction, as this shapes metric selection.

2. Define engagement dimensions

Break engagement into active (e.g., likes, comments, shares), passive (e.g., watch time), and retention (e.g., return frequency) to cover the full spectrum.

3. Select top metrics

Choose three metrics that balance these dimensions, such as average watch time per user, daily active users (DAU) or session frequency, and interaction rate (likes/comments/shares per view).

4. Justify and contextualize

Explain why each metric matters, how they complement each other, and how they might be gamed or misused, suggesting guardrails.

5. Tie to experimentation

Mention how you would validate these metrics through A/B tests and monitor them alongside counter-metrics to ensure healthy engagement.

Key Points to Mention

  • Average watch time per user or per session as a measure of content quality and passive engagement.
  • Daily active users (DAU) or 7-day retention rate to capture habitual usage and long-term engagement.
  • Interaction rate (likes, comments, shares per view) to gauge active engagement and social validation.
  • Session frequency or sessions per user per day to understand depth of engagement.
  • Guardrail metrics like user-reported satisfaction or churn to avoid optimizing for vanity metrics.
  • A/B testing framework to validate metric sensitivity and alignment with business goals.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.

Q2

Design an A/B test for a new recommendation algorithm: walk through how you'd calculate sample size, decide on experiment duration, and define stopping criteria.

A/B Testing & ExperimentationProduct Analytics & Metrics
Author's notes

This is where I stumbled a bit.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal and primary metric (e.g., CTR or engagement), then walk through the statistical steps: define hypotheses, calculate sample size using power analysis, determine duration based on traffic and novelty effects, and set stopping criteria that balance statistical rigor with practical constraints. Emphasize the importance of pre-registration and avoiding peeking to maintain validity.

Pro tip: At Meta, always consider the network effects and potential interference between users in social experiments; mention using cluster-based randomization or switchback tests when appropriate. Also, be prepared to discuss how you'd handle multiple testing corrections if you're evaluating multiple metrics.

1. Define Hypothesis and Metrics

Clearly state the null and alternative hypotheses, and select a primary metric (e.g., click-through rate) along with guardrail metrics (e.g., user satisfaction, latency).

2. Calculate Sample Size

Use power analysis: specify significance level (α=0.05), power (1-β=0.8), minimum detectable effect (MDE), and baseline variance to compute required sample size per variant.

3. Determine Experiment Duration

Estimate daily traffic to the experiment, divide required sample size by daily traffic to get minimum days, then adjust for weekly seasonality and novelty effects (e.g., run for at least 1-2 weeks).

4. Set Stopping Criteria

Pre-register stopping rules: either fixed-horizon (stop after reaching sample size) or sequential testing with alpha-spending to allow early stopping for efficacy/futility while controlling Type I error.

5. Analyze and Decide

After experiment concludes, perform statistical tests (e.g., t-test or bootstrap) on primary metric, check guardrails, and consider practical significance before making a ship/no-ship decision.

Key Points to Mention

  • Power analysis: α, β, MDE, and variance
  • Sample size formula for proportions or means
  • Novelty effect and primacy effect
  • Multiple testing correction (e.g., Bonferroni, FDR)
  • Sequential testing and alpha spending
  • Network effects and interference in social experiments

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.