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Meta·Data Scientist·Technical Phone Screen·Senior

Senior
Jul 2026

Summary

Meta DS interview focused entirely on trust and safety measurement. The whole thing was one long case about building a metrics framework and then designing an experiment for a harmful content detection system. Pretty intense if you haven't thought carefully about harm-weighted metrics before.

Questions Asked (3)

Q1

Propose metrics to measure both the severity and prevalence of inappropriate content on the platform. For each metric, explain your reasoning and walk through the tradeoffs.

Product Analytics & MetricsProduct Sense & Ideation
Author's notes

This is where I stumbled a bit.

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AI HintsAI Generated

Suggested Approach

Start by defining inappropriate content and clarifying the distinction between severity (how harmful a piece of content is) and prevalence (how widespread it is). Then propose metrics for each dimension, such as a severity score and prevalence rate, and discuss tradeoffs like accuracy vs. scalability and user impact vs. operational cost.

Pro tip: Acknowledge that perfect measurement is impossible due to the subjective nature of inappropriateness and the need for human review; propose a hybrid approach combining automated classifiers with human audits to calibrate and validate metrics.

1. Define inappropriate content and scope

Clarify what types of content are considered inappropriate (e.g., hate speech, harassment, misinformation) and the platform surfaces (posts, comments, messages). This ensures metrics are aligned with policy and user expectations.

2. Propose severity metrics

Develop metrics that capture the harm level of individual content items, such as a severity score from a trained model or human rating, and aggregate metrics like average severity per user or percentage of high-severity content.

3. Propose prevalence metrics

Define metrics that measure how common inappropriate content is, such as prevalence rate (number of violating items per 10,000 views) or user exposure rate (percentage of users who encounter inappropriate content).

4. Discuss tradeoffs and validation

For each metric, explain tradeoffs: severity scores may be subjective and hard to scale, while prevalence metrics can be gamed by removal speed. Discuss validation via human audits and the need for confidence intervals.

5. Prioritize and operationalize

Recommend which metrics to prioritize based on business goals (e.g., reducing severe harm vs. overall prevalence) and how to operationalize them with dashboards, alerts, and regular reviews.

Key Points to Mention

  • Distinguish between severity (intensity of harm) and prevalence (frequency/scale) and why both matter.
  • Use a combination of automated classifiers and human review to measure severity, acknowledging subjectivity.
  • Define prevalence as a rate (e.g., per 10,000 views) to account for platform growth and engagement.
  • Consider tradeoffs: precision vs. recall in detection, cost of human review, and potential bias in models.
  • Validate metrics with human audits and track changes over time to ensure reliability.
  • Align metrics with business objectives, such as reducing user harm or complying with regulations.

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

Q2

Define the View Prevalence metric and justify why it's the right way to measure content exposure.

Product Analytics & Metrics
Author's notes

View Prevalence is basically the share of content views that land on violating content rather than the share of posts that violate policy.

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AI HintsAI Generated

Suggested Approach

Start by clearly defining View Prevalence as the proportion of content impressions that are actually viewed by users, then explain why it's a more accurate measure of exposure than raw impressions or clicks. Justify its superiority by linking it to user attention, engagement quality, and business outcomes like ad effectiveness or content ranking.

Pro tip: Acknowledge that View Prevalence is not a one-size-fits-all metric; discuss how thresholds for what counts as a 'view' can vary by content type and platform, and how this flexibility makes it adaptable but requires careful calibration.

1. Define View Prevalence

Define View Prevalence as the ratio of viewed impressions to total impressions, where a 'view' is typically defined by a minimum time threshold (e.g., 3 seconds) or interaction. Clarify that it measures the fraction of served content that actually receives user attention.

2. Contrast with Alternative Metrics

Compare View Prevalence to raw impressions (which count serves regardless of view) and click-through rates (which only capture explicit clicks). Highlight that View Prevalence captures passive exposure that impressions miss and includes non-clicked but viewed content.

3. Justify as a Measure of Exposure

Argue that View Prevalence directly quantifies attention, making it a better proxy for actual exposure than impression counts. Explain that it aligns with how users consume content (often passively) and reflects the true reach of content.

4. Connect to Business Impact

Link View Prevalence to key business outcomes: higher view prevalence indicates more effective content delivery, better ad performance, and improved user engagement. Emphasize its role in optimizing ranking algorithms and ad pricing.

5. Address Limitations and Nuances

Acknowledge that View Prevalence depends on the definition of a 'view' and may vary across contexts. Discuss how to set thresholds and handle edge cases (e.g., auto-play, background views) to maintain metric validity.

Key Points to Mention

  • Definition of a 'view' (e.g., 3-second threshold, pixel coverage, interaction)
  • Difference between impressions, views, and clicks
  • View Prevalence as a ratio (viewed impressions / total impressions)
  • Alignment with user attention and engagement quality
  • Impact on ad effectiveness and content ranking algorithms
  • Potential pitfalls: view threshold sensitivity, bot traffic, viewability standards

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

Q3

Design an A/B experiment to evaluate a new harmful content detection model. Cover your hypothesis, primary metric, guardrails, sample size and runtime estimates, and how you'd interpret the results.

A/B Testing & ExperimentationProduct Analytics & MetricsTechnical Trade-offs
Author's notes

Long question and I tried to answer it all at once which was a mistake.

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AI HintsAI Generated

Suggested Approach

Structure your answer around a clear experiment design: start with a well-defined hypothesis and primary metric, then discuss guardrails, sample size calculation, runtime, and interpretation. Emphasize the trade-offs between precision and recall for harmful content detection, and how you'd measure success while minimizing user harm.

Pro tip: For harmful content detection, the primary metric should balance precision and recall, but also consider the cost of false negatives (harmful content shown) vs false positives (over-censorship). Propose a composite metric like 'harmful content prevalence' or 'user reports per 1000 views' to capture the overall health of the platform.

1. Define Hypothesis and Metrics

State a clear hypothesis: the new model reduces harmful content prevalence without increasing false positives. Choose a primary metric (e.g., prevalence of harmful content) and secondary metrics (e.g., precision, recall, user reports).

2. Identify Guardrails

List guardrail metrics that must not degrade: user engagement, false positive rate (over-censorship), and system latency. These ensure the new model doesn't harm user experience or platform health.

3. Calculate Sample Size and Runtime

Estimate baseline prevalence and desired minimum detectable effect (MDE). Use power analysis to determine sample size per variant, then translate to runtime based on daily traffic. Consider stratification by content type or user segment.

4. Design Experiment and Randomization

Decide randomization unit (e.g., user, content item, or session). Ensure proper randomization and avoid contamination. Consider a holdout group for long-term effects.

5. Interpret Results and Make Decision

Analyze primary metric with statistical significance, check guardrails, and consider practical significance. If primary improves and guardrails hold, recommend rollout; otherwise, iterate or reject.

Key Points to Mention

  • Define harmful content clearly and how it's measured (e.g., human labels, user reports).
  • Use a composite metric or multiple metrics to capture both precision and recall trade-offs.
  • Consider the cost of false negatives (harmful content shown) vs false positives (over-censorship).
  • Account for seasonality or external events that might affect harmful content prevalence.
  • Ensure sufficient power by calculating sample size based on baseline prevalence and MDE.
  • Monitor guardrails like user engagement and false positive rate to avoid unintended harm.

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