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Meta·Data Scientist·Technical Phone Screen·Senior

Senior
Jun 2026

Summary

Two-part Meta DS interview focused entirely on feed personalization. Part A was a deep causal inference design problem, Part B was a full A/B experiment spec. No behavioral questions, no SQL, just two very meaty open-ended cases back to back.

Questions Asked (2)

Q1

Using impression-level and interaction-level logs plus a friendships graph, design an analysis to validate whether friends' content drives more social engagement than unconnected content in a personalized feed. Cover how you'd define a 'socialness' outcome, justify action weights, control for ranking confounds, and specify your effect estimates and statistical approach.

Product Analytics & MetricsA/B Testing & ExperimentationData Modeling
Author's notes

This is the kind of question where you can talk for 20 minutes and still feel like you barely scratched the surface.

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AI HintsAI Generated

Suggested Approach

Start by defining a composite 'socialness' outcome using impression and interaction logs, with action weights derived from a utility model or empirical engagement value. Then design a quasi-experimental analysis that controls for ranking confounds via propensity score matching or inverse propensity weighting, and estimate the causal effect of friend content on social engagement using a regression with fixed effects or a difference-in-differences approach.

Pro tip: Emphasize that ranking confounds are the biggest threat to validity; propose using the ranking model's features as covariates or leveraging a randomized holdout in the ranking system to create a clean comparison.

1. Define Socialness Outcome

Construct a composite engagement metric that captures social interactions (e.g., likes, comments, shares) weighted by their estimated value, using impression-level logs to attribute actions to content.

2. Justify Action Weights

Derive weights from a utility model (e.g., willingness to pay, long-term value) or empirically from downstream outcomes like retention, ensuring they reflect true social value.

3. Control for Ranking Confounds

Use propensity score matching or inverse propensity weighting based on ranking features, or exploit a randomized ranking holdout, to isolate the effect of friend content from ranking bias.

4. Estimate Effect

Fit a regression model with user and content fixed effects, or a difference-in-differences design, to estimate the average treatment effect of friend content on the socialness outcome.

5. Statistical Validation

Conduct robustness checks, sensitivity analyses, and significance testing (e.g., bootstrap confidence intervals) to ensure the effect is not driven by unobserved confounders.

Key Points to Mention

  • Use of impression-level and interaction-level logs to track user actions and content exposure.
  • Friendships graph to identify friend vs. non-friend content.
  • Definition of socialness as a weighted sum of social actions (likes, comments, shares).
  • Action weights derived from utility theory or empirical long-term value.
  • Ranking confounds controlled via propensity scores or randomized holdout.
  • Causal inference methods: fixed effects, difference-in-differences, or instrumental variables.

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

Q2

You're launching unconnected content into a feed that previously only showed friends' posts. Define success metrics and design an A/B experiment that accounts for network interference, novelty effects, and potential cannibalization of friends' content. Include your randomization unit, ramp plan, power calculations, primary KPIs, guardrails, and a rollout or rollback framework.

A/B Testing & ExperimentationProduct Analytics & MetricsProduct Strategy
Author's notes

Honestly the harder of the two for me.

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AI HintsAI Generated

Suggested Approach

Start by framing the product goal and defining success metrics that capture both user engagement and ecosystem health. Then design an A/B experiment with a randomization unit that minimizes interference, and outline a ramp plan with power calculations, guardrails, and a rollout/rollback framework. Explicitly address novelty effects and cannibalization through measurement and mitigation strategies.

Pro tip: Propose using a cluster-randomized design (e.g., by user or social graph cluster) to account for network interference, and pre-register a holdback group to measure long-term novelty decay and cannibalization.

1. Define Success Metrics

Identify primary KPIs (e.g., unconnected content engagement, overall feed engagement, user retention) and guardrail metrics (e.g., friends' content engagement, user satisfaction, report rate). Include both short-term and long-term indicators.

2. Design Experiment with Interference in Mind

Choose a randomization unit (e.g., user, household, or social cluster) that reduces spillover effects. Consider cluster randomization or switchback designs if interference is high. Define treatment and control groups clearly.

3. Plan Ramp and Power Calculations

Determine sample size and duration using power analysis, accounting for intra-cluster correlation if using cluster randomization. Plan a gradual ramp (e.g., 1%, 5%, 10%, 50%) to monitor early signals and limit risk.

4. Address Novelty and Cannibalization

Include a long-term holdout to measure novelty decay. Analyze cannibalization by tracking friends' content engagement and overall time spent. Use difference-in-differences or cohort analysis to separate novelty from sustained effects.

5. Establish Rollout/Rollback Framework

Define go/no-go criteria based on primary KPIs and guardrails. Set up automated monitoring and alerts for guardrail violations. Outline a rollback plan if negative impacts are detected, and a phased rollout if successful.

Key Points to Mention

  • Network interference and cluster randomization to mitigate spillover effects
  • Novelty effect measurement via long-term holdout and cohort analysis
  • Cannibalization metrics: friends' content engagement, overall feed time, user satisfaction
  • Power calculations accounting for intra-cluster correlation and minimum detectable effect
  • Guardrail metrics and automated monitoring for safe ramp
  • Rollout/rollback criteria and phased ramp plan

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