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Meta·Data Scientist·Technical Phone Screen·Senior

Senior
May 2026

Summary

A product DS case for Meta's feed team. The whole thing was one big multi-part scenario about introducing unconnected content into the Info Stream, and it went pretty deep into experiment design, metric tradeoffs, and what to do when your results are messy.

Questions Asked (4)

Q1

Using impression, view, and reaction data, how would you validate that content from a user's friends drives stronger engagement than content from unconnected authors? Walk through the metrics you'd define, your hypotheses, and how you'd control for confounders like feed position and content type.

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

This is where I spent most of my time and also where I stumbled a bit.

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AI HintsAI Generated

Suggested Approach

Start by defining clear engagement metrics (e.g., impression-to-view rate, view-to-reaction rate) and formulate a hypothesis that friend content drives higher engagement. Then propose an experimental design (e.g., A/B test or holdout) that randomizes feed position and content type to isolate the effect, and use regression or matching to control for confounders.

Pro tip: Emphasize the importance of controlling for feed position by randomizing it or using a within-subject design, as position bias is a major confounder in feed ranking. Also, consider using causal inference methods like propensity score matching if randomization is not feasible.

1. Define Metrics and Hypotheses

Clearly define engagement metrics such as impression-to-view rate, view-to-reaction rate, and overall engagement rate. State the null and alternative hypotheses: H0: friend content does not drive stronger engagement than unconnected authors; H1: friend content drives stronger engagement.

2. Design Experiment to Control Confounders

Propose an A/B test where users are randomly assigned to see friend content in higher or lower feed positions, or use a within-subject design where each user sees both types of content in randomized positions. Ensure content type is balanced across conditions.

3. Collect and Analyze Data

Collect impression, view, and reaction data for each content type and position. Use statistical tests (e.g., t-test, ANOVA) or regression models (e.g., logistic regression) to compare engagement metrics while controlling for feed position, content type, and user-level random effects.

4. Validate and Interpret Results

Check for statistical significance and effect size. Conduct sensitivity analyses to ensure robustness (e.g., different model specifications, subgroup analyses). Interpret whether the effect is practically significant and consider potential biases.

5. Communicate Findings and Limitations

Summarize results, highlighting the controlled comparison and any remaining limitations (e.g., generalizability, unmeasured confounders). Suggest next steps for further validation or product implications.

Key Points to Mention

  • Definition of engagement metrics: impression-to-view rate, view-to-reaction rate, and overall engagement rate.
  • Hypothesis testing framework with null and alternative hypotheses.
  • Experimental design: A/B test or within-subject randomization to control for feed position and content type.
  • Statistical methods: regression models, ANOVA, or causal inference techniques like propensity score matching.
  • Control for confounders: feed position, content type, user demographics, time of day, and content quality.
  • Consideration of practical significance and effect size, not just statistical significance.

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

Q2

Design an experiment to measure whether launching unconnected content into the feed is successful. Cover randomization unit, treatment arms, experiment duration, statistical power, primary success metrics, and guardrail metrics.

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

I got the basics right: user-level randomization, a control arm with zero unconnected content and a few treatment arms with different insertion rates.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the goal: unconnected content aims to increase discovery and engagement, but may reduce relevance. Then outline a randomized controlled experiment with user-level randomization, multiple treatment arms (e.g., control, low, high unconnected content), and define primary metrics (e.g., time spent, content diversity) and guardrails (e.g., user satisfaction, hide/report rates). Finally, discuss power analysis, duration, and potential network effects.

Pro tip: Emphasize the importance of pre-registering the analysis plan and considering long-term effects via holdout groups, as short-term gains may not persist. Also, mention that unconnected content might have heterogeneous effects across user segments, so plan for subgroup analyses.

1. Clarify Objective and Hypotheses

Define what 'success' means for unconnected content: increased discovery, engagement, or retention. State null and alternative hypotheses for the experiment.

2. Design Randomization and Treatment Arms

Choose user-level randomization to avoid interference. Set up control (no unconnected content) and treatment arms with varying proportions of unconnected content (e.g., 10%, 30%).

3. Select Metrics and Determine Sample Size

Identify primary success metrics (e.g., time spent, likes, comments, shares) and guardrail metrics (e.g., hide/report rates, user satisfaction, churn). Conduct power analysis to determine sample size and duration.

4. Run Experiment and Monitor

Launch the experiment, monitor for data quality, and ensure no SRM (sample ratio mismatch). Track guardrails continuously to catch negative effects early.

5. Analyze Results and Make Recommendations

Perform statistical tests (e.g., t-tests, bootstrapping) on primary and guardrail metrics. Consider heterogeneous treatment effects and long-term impact. Provide clear recommendation based on trade-offs.

Key Points to Mention

  • Randomization unit: user-level to prevent contamination and network effects.
  • Treatment arms: control, low unconnected content, high unconnected content.
  • Primary metrics: time spent, content diversity, engagement rate (likes/comments/shares).
  • Guardrail metrics: hide/report rate, user satisfaction (surveys), churn/retention, session frequency.
  • Experiment duration: at least one week to capture weekly patterns, but based on power analysis.
  • Statistical power: 80% power, 5% significance, minimum detectable effect (MDE) determined from historical data.

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

Q3

How would you interpret the experiment results, including potential cannibalization of friend engagement and segmentation effects? What would your launch decision and rollout plan look like?

A/B Testing & ExperimentationProduct Strategy
Author's notes

Cannibalization is the sneaky part here.

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AI HintsAI Generated

Suggested Approach

Start by framing the experiment's primary metric and guardrails, then interpret results with a focus on cannibalization and heterogeneous treatment effects. Use segmentation to identify where the treatment works best and worst, and propose a phased rollout that maximizes net impact while mitigating risks.

Pro tip: Always quantify the trade-off between the primary metric and cannibalized metrics in terms of net top-line impact, and recommend a holdout or long-term measurement to validate sustained effects.

1. Clarify Metrics and Hypotheses

Restate the primary success metric, guardrail metrics (e.g., friend engagement), and the hypothesis about cannibalization. Confirm the experiment design and analysis plan.

2. Analyze Overall and Segmented Effects

Examine overall treatment effect on primary and guardrail metrics. Then segment by key dimensions (e.g., user demographics, friend network density) to detect heterogeneous treatment effects and cannibalization patterns.

3. Quantify Cannibalization and Net Impact

Estimate the degree of cannibalization (e.g., reduction in friend engagement) and compute the net effect on the top-line metric. Use statistical tests to determine if cannibalization is significant and material.

4. Make Launch Decision and Rollout Plan

Based on net impact and segmentation, decide whether to launch, iterate, or abandon. If launching, propose a phased rollout (e.g., start with segments with highest net positive impact) and define success criteria for each phase.

5. Recommend Monitoring and Iteration

Outline a plan to monitor key metrics post-launch, including long-term holdout groups to detect delayed effects. Suggest further experiments to optimize for segments with negative or neutral impact.

Key Points to Mention

  • Cannibalization: define it as the negative impact on friend engagement due to the treatment, and measure it via guardrail metrics.
  • Segmentation: analyze by user activity level, friend network size, and demographics to find heterogeneous effects.
  • Net impact: calculate the combined effect on primary and guardrail metrics to assess overall value.
  • Statistical significance: ensure results are not due to chance, and consider multiple testing corrections for segments.
  • Phased rollout: start with segments showing strong positive net impact, then expand gradually while monitoring.
  • Long-term holdout: maintain a control group to measure sustained effects and avoid novelty effects.

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

Q4

If unconnected viewers show lower per-impression engagement, what alternative value could they still provide, and how would you quantify it?

Product Analytics & MetricsProduct Sense & Ideation
Author's notes

Favorite part of the whole case, weirdly.

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AI HintsAI Generated

Suggested Approach

Acknowledge that unconnected viewers may have lower per-impression engagement, but reframe their value by identifying alternative contributions such as reach, network effects, and long-term potential. Then propose a quantification framework that measures these indirect and downstream effects, using metrics like incremental reach, lift in connected user engagement, and predicted lifetime value.

Pro tip: Show that you understand the difference between correlation and causation—unconnected viewers might be lower-engagement because they are new or less targeted, not because they are inherently less valuable. Quantify their value by measuring the incremental impact they have on the ecosystem, not just their direct engagement.

1. Identify alternative value dimensions

Brainstorm non-engagement values such as reach, brand exposure, social influence, content discovery, and future conversion potential. Consider both direct and indirect benefits to the platform.

2. Define quantifiable proxies

For each value dimension, define measurable proxies (e.g., incremental reach, ad recall lift, network growth, or predicted future engagement). Ensure they are trackable with available data.

3. Design measurement approach

Propose experiments or observational methods (e.g., A/B tests, holdout groups, causal inference) to isolate the incremental value of unconnected viewers. Account for selection bias.

4. Estimate long-term value

Use predictive modeling to estimate the lifetime value of unconnected viewers, including their potential to become connected and influence others. Incorporate retention and conversion rates.

5. Synthesize into a unified metric

Combine direct and indirect value into a single metric (e.g., total value per viewer) to compare with connected viewers. Communicate assumptions and limitations.

Key Points to Mention

  • Reach and frequency as a value for advertisers, even without engagement.
  • Network effects: unconnected viewers may attract or influence connected users.
  • Long-term potential: unconnected viewers can become connected and highly engaged over time.
  • Incremental lift: measure the causal impact of unconnected viewers on overall platform metrics.
  • Use of holdout experiments or propensity score matching to quantify indirect effects.
  • Lifetime value (LTV) modeling to capture future revenue from unconnected viewers.

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