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TikTok·Data Scientist·Hiring Manager Screen·Senior

Senior
Jun 2026

Summary

TikTok data scientist interview that went deep on product diagnostics and causal inference. Two meaty questions, both from a manager framing, so the expectation was clearly less about code and more about how you think through messy real-world data problems.

Questions Asked (2)

Q1

Daily active users have been declining steadily for several weeks. What metrics would you define and what analysis or experiment would you design to figure out what's going wrong?

Product Analytics & MetricsRoot Cause AnalysisA/B Testing & Experimentation
Author's notes

This is the kind of question where you can ramble forever if you're not careful.

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AI HintsAI Generated

Suggested Approach

Start by defining a metric tree that breaks down DAU into its components (new, retained, resurrected users) and segments (platform, region, content type). Then systematically analyze each component to identify the source of decline, and design targeted experiments to test hypotheses about root causes.

Pro tip: Always validate metric definitions and data quality first—declines are often due to tracking bugs or seasonality. Also, consider external factors like competitor launches or app store changes before diving into product changes.

1. Define and Validate Metrics

Define DAU precisely (e.g., unique users who open the app daily) and break it down into acquisition, retention, and resurrection metrics. Validate data pipelines to rule out tracking issues.

2. Segment and Localize the Decline

Slice DAU by dimensions like platform (iOS/Android), region, user tenure, and content categories to identify where the decline is concentrated. Use cohort analysis to see if specific cohorts are driving the drop.

3. Form and Test Hypotheses

Generate hypotheses based on segments (e.g., a new feature caused churn, algorithm change reduced engagement). Use funnel analysis, retention curves, and engagement metrics (time spent, videos viewed) to narrow down causes.

4. Design Experiments to Confirm Causality

If a hypothesis points to a product change, design an A/B test or quasi-experiment (e.g., holdout groups, switchback tests) to measure impact. Ensure proper power analysis and guardrail metrics.

5. Recommend Actions and Monitor

Based on findings, recommend fixes (e.g., revert feature, improve onboarding) and set up dashboards to monitor recovery. Define success metrics and iterate if needed.

Key Points to Mention

  • Metric tree: DAU = New + Retained + Resurrected - Churned
  • Segmentation by platform, region, user cohort, and content type
  • Cohort analysis and retention curves to identify when users drop off
  • Funnel analysis (e.g., sign-up to first video view) to pinpoint friction
  • A/B testing with proper control groups and guardrail metrics
  • External factors: seasonality, competitor actions, app store policy changes

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

Q2

A manager wants to understand how network speed causally affects TikTok usage, but you only have observational data. What causal inference method would you use, and how would you explain why it's valid to someone non-technical?

Product Analytics & MetricsRoot Cause AnalysisA/B Testing & Experimentation
Author's notes

This one tripped me up more than I expected.

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AI HintsAI Generated

Suggested Approach

Start by acknowledging the challenge of causal inference with observational data, then propose a method like instrumental variables or propensity score matching, and finally explain its validity using a simple analogy that a non-technical person can grasp.

Pro tip: Emphasize that while observational methods can provide strong evidence, they rely on assumptions; always validate with sensitivity analysis and, if possible, complement with a small-scale experiment.

1. Identify the causal question and data limitations

Clarify that the goal is to estimate the causal effect of network speed on TikTok usage, and note that observational data may have confounding factors like user demographics or time of day.

2. Choose an appropriate causal inference method

Select a method such as instrumental variables (e.g., using distance to cell towers as an instrument for network speed) or propensity score matching to control for confounders.

3. Explain the method's validity in simple terms

Use an analogy: like comparing two groups of people who are similar in all ways except network speed, to isolate the effect of speed on usage.

4. Discuss assumptions and limitations

Mention key assumptions (e.g., the instrument affects usage only through network speed) and suggest sensitivity checks to ensure robustness.

5. Recommend validation and next steps

Propose running a small randomized experiment or using natural experiments to confirm findings, and communicate results with confidence intervals.

Key Points to Mention

  • Confounding variables and the need to control for them
  • Instrumental variables or propensity score matching as methods
  • The importance of assumptions (e.g., exclusion restriction)
  • Using analogies to explain causality to non-technical stakeholders
  • Sensitivity analysis to test robustness
  • Complementing observational studies with experiments when possible

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