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TikTok·Data Scientist·Technical Phone Screen·Senior

SeniorPrefer not to say
Jul 2026

Summary

TikTok data scientist interview focused heavily on e-commerce advertising analytics, covering everything from metric design to A/B testing to diagnosing revenue drops. Pretty case-heavy, less coding than I expected.

Questions Asked (3)

Q1

Walk me through one of your resume projects: what success metrics did you define, how did you measure them, and what did your A/B experiment design look like?

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

I picked a project I thought was solid but fumbled the experiment design part a bit.

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AI HintsAI Generated

Suggested Approach

Choose a project where you owned the metrics and experiment design end-to-end, ideally with a clear product impact. Structure your answer using a STAR-like narrative but emphasize the metric definition, measurement methodology, and A/B test design details. Quantify outcomes and highlight trade-offs or learnings to show depth.

Pro tip: TikTok values rapid experimentation and user engagement metrics, so frame your success metrics around user behavior (e.g., watch time, retention) and mention how you ensured statistical power and avoided common pitfalls like peeking or multiple testing.

1. Set the context and goal

Briefly describe the project, your role, and the business objective. Explain why defining success metrics was critical for this project.

2. Define success metrics

List the primary and secondary metrics you chose, and justify why they align with the business goal. Mention how you ensured they were measurable and sensitive to change.

3. Explain measurement methodology

Describe how you collected and processed data, including any instrumentation, logging, or data pipeline considerations. Highlight steps to ensure data quality and avoid bias.

4. Detail the A/B experiment design

Outline the hypothesis, randomization unit, sample size calculation, duration, and control/treatment setup. Discuss how you monitored the experiment and handled any issues.

5. Share results and learnings

Present the outcome: statistical significance, effect size, and impact on metrics. Reflect on what you learned and how you would improve future experiments.

Key Points to Mention

  • Clear hypothesis and alignment with business objectives
  • Primary and guardrail metrics (e.g., watch time, retention, click-through rate)
  • Sample size calculation and power analysis to ensure statistical validity
  • Randomization unit (e.g., user-level) and potential network effects
  • Statistical tests used (e.g., t-test, sequential testing) and handling of multiple comparisons
  • Practical significance vs. statistical significance and impact on product decisions

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

Q2

The business wants to grow merchant advertising revenue or merchant GMV. How would you approach diagnosing the current state and recommending actions?

Product Analytics & MetricsProduct StrategyPricing & Monetization
Author's notes

This one felt open-ended in a way that stressed me out at first.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the business objective and defining the key metrics that drive merchant advertising revenue and GMV. Then, structure your answer around a diagnostic framework that segments merchants, analyzes funnel performance, and identifies levers for growth. Finally, recommend actionable strategies prioritized by impact and feasibility, and suggest how to measure their effectiveness.

Pro tip: Emphasize the importance of understanding merchant lifetime value and the interplay between advertising spend and organic GMV to avoid cannibalization. Also, mention the need for experimentation (A/B tests) to validate recommendations.

1. Clarify Objectives and Metrics

Define what 'grow merchant advertising revenue or merchant GMV' means: is it total revenue, GMV, or both? Identify key metrics like ad spend per merchant, ROAS, GMV per merchant, and conversion rates.

2. Segment Merchants and Analyze Funnel

Segment merchants by size, category, and performance. Analyze the funnel from ad exposure to conversion to identify drop-offs and opportunities for each segment.

3. Diagnose Root Causes

Use data to pinpoint why certain segments underperform: e.g., low ad adoption, poor targeting, budget constraints, or seasonal effects. Compare against benchmarks and historical trends.

4. Recommend Actions and Prioritize

Propose targeted interventions such as personalized ad recommendations, incentive programs, or improved targeting. Prioritize based on estimated impact and effort.

5. Measure and Iterate

Suggest A/B tests or pilot programs to validate actions. Define success metrics and a process for scaling successful initiatives.

Key Points to Mention

  • Merchant segmentation (e.g., by size, industry, ad spend) to tailor strategies
  • Funnel analysis from ad impression to conversion to identify bottlenecks
  • ROAS and its relationship with GMV to ensure sustainable growth
  • Potential cannibalization between ads and organic content
  • Incentives for merchants to increase ad spend (e.g., matching credits, performance bonuses)
  • Experimentation framework (A/B testing) to measure incremental lift

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

Q3

Ad ROI has been declining recently. How would you investigate why, and what fixes would you propose?

Root Cause AnalysisProduct Analytics & MetricsA/B Testing & Experimentation
Author's notes

Classic root cause question but the advertising angle made it trickier than usual.

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AI HintsAI Generated

Suggested Approach

Start by clarifying what 'ROI' means in this context—likely return on ad spend (ROAS) or a similar metric—and confirm the time frame and scope of the decline. Then systematically break down the metric into its components (e.g., revenue per ad dollar, conversion rates, CPMs) to isolate the root cause, considering internal changes, external factors, and data quality issues. Finally, propose targeted fixes based on the diagnosis, prioritizing A/B tests to validate solutions.

Pro tip: Demonstrate a hypothesis-driven approach by suggesting you'd first check for data pipeline or tracking issues before assuming a real decline, as data quality problems are a common culprit in ad metrics. Also, emphasize the importance of segmenting by user cohorts, ad formats, and regions to avoid Simpson's paradox.

1. Define and Validate the Metric

Clarify the exact definition of ad ROI (e.g., ROAS = revenue / ad spend) and verify the decline is real by checking data quality, tracking changes, and ensuring consistent calculation methods.

2. Decompose the Metric

Break down ROI into its drivers: ad spend, impressions, clicks, conversion rate, average order value, etc. Use a tree diagram to identify which component(s) changed and contributed most to the decline.

3. Segment and Compare

Slice the data by dimensions such as time, user demographics, ad format, placement, region, and device to pinpoint where the decline is concentrated. Compare against benchmarks and historical trends.

4. Generate and Test Hypotheses

List potential causes (e.g., increased competition, ad fatigue, algorithm changes, seasonality, macroeconomic factors) and prioritize them based on data. Use A/B tests or quasi-experimental methods to validate the most likely causes.

5. Propose and Prioritize Fixes

Based on the root cause, suggest actionable fixes such as creative refresh, targeting adjustments, bid strategy changes, or budget reallocation. Estimate impact and effort to prioritize, and recommend A/B tests to measure effectiveness.

Key Points to Mention

  • Data quality checks: ensure tracking pixels, attribution windows, and ETL pipelines are functioning correctly before assuming a real decline.
  • Metric decomposition: use a formula like ROI = (Conversion Rate * Average Order Value) / Cost Per Click to isolate drivers.
  • Segmentation: analyze by user cohorts, ad formats (e.g., Spark Ads vs. non-native), geographies, and time periods to uncover hidden patterns.
  • External factors: consider seasonality, competitor activity, platform algorithm updates, and macroeconomic trends.
  • A/B testing: propose controlled experiments to validate fixes, ensuring proper randomization, sample size, and guardrail metrics.
  • Stakeholder alignment: collaborate with marketing, product, and engineering teams to gather context and implement solutions.

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