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Coinbase·Data Scientist·Technical Phone Screen·Senior

Senior
May 2026

Summary

Coinbase data science interview with a product analytics case built around a Super Bowl QR code ad. The whole thing was one big funnel estimation problem, which sounds manageable until you realize they want you to handle missing data from a third-party agency too.

Questions Asked (3)

Q1

During a Super Bowl broadcast, a QR code appears in a TV ad. What percentage of viewers do you think would actually scan it, and how would you use historical data to build that estimate?

Product Analytics & MetricsAdaptability & Ambiguity
Author's notes

I started by trying to anchor on something concrete: what's the baseline attention rate for a Super Bowl ad, then layer on the friction of grabbing your phone and scanning mid-broadcast.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the context and assumptions (e.g., Super Bowl viewership, ad placement, QR code prominence) and then propose a structured estimation method using historical benchmarks and analogous data. Walk through a funnel-based calculation (impressions → scans → conversions) and emphasize how you would validate and refine the estimate with A/B tests or post-campaign analysis.

Pro tip: Acknowledge that the actual Coinbase Super Bowl QR code campaign saw a massive spike in traffic, but avoid quoting exact numbers unless you can cite them; instead, focus on the methodology and how you'd use historical data like past QR code campaigns, CTRs, and scan rates to build a defensible estimate.

1. Clarify the scenario and assumptions

Ask clarifying questions about the ad (e.g., duration, placement, call-to-action) and define the target audience (e.g., US viewers, demographics). State assumptions explicitly, such as Super Bowl viewership (~100M) and the percentage of viewers with a smartphone ready.

2. Identify relevant historical data

List internal and external data sources: past QR code campaigns (e.g., other Super Bowl ads, Snapchat codes), industry benchmarks for CTR on TV ads, and website traffic spikes from similar events. Consider Coinbase's own historical campaign data if available.

3. Build a funnel-based estimate

Break down the estimation into stages: total viewers → viewers who see the ad → viewers with a smartphone → viewers motivated to scan → successful scans. Assign plausible conversion rates at each stage based on historical data and adjust for novelty/context.

4. Validate and refine with data

Propose methods to validate the estimate: A/B testing (e.g., different QR code placements), post-campaign analysis of actual scan data, and comparing with control periods. Discuss how to use real-time data to adjust the estimate during the campaign.

5. Communicate uncertainty and business impact

Present the estimate as a range (e.g., 0.5%–2%) with confidence intervals, and tie it to business metrics like sign-ups or revenue. Highlight the importance of adaptability and learning from the actual outcome to improve future estimates.

Key Points to Mention

  • Super Bowl viewership (~100 million) and the percentage of viewers who are actively watching the ad (not second-screening).
  • Historical QR code scan rates from similar high-profile events (e.g., other Super Bowl ads, Snapchat codes) and industry benchmarks for TV ad CTR.
  • Funnel-based estimation: from total viewers to scans, with conversion rates at each stage (e.g., 10% see the QR code, 1% scan it).
  • The novelty effect: a QR code in a Super Bowl ad is unusual, so scan rates might be higher than typical, but also limited by technical friction.
  • Methods to validate: A/B testing, post-campaign analysis, and comparing with control groups or historical traffic patterns.
  • Business impact: how the scan rate translates to sign-ups, revenue, and ROI, and how to use the data to inform future campaigns.

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

Q2

If the conversion rate data from previous QR campaigns belongs to the ad agency and you only have access to TV-side data, how do you still approximate the scan rate?

Product Analytics & MetricsRoot Cause Analysis
Author's notes

This is where I fumbled a bit.

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AI HintsAI Generated

Suggested Approach

Acknowledge the data limitation and propose a triangulation approach using TV-side data and external benchmarks to estimate scan rate. Focus on deriving a defensible range rather than a precise number, and validate assumptions with sensitivity analysis.

Pro tip: Emphasize that scan rate is a function of both ad exposure and user intent; use TV-side proxies like reach and frequency to model exposure, and clearly state assumptions to build credibility. Show awareness that the agency's data might be accessible via negotiation or privacy-preserving methods like aggregated reporting.

1. Clarify the objective and constraints

Confirm whether the goal is a rough estimate for planning or a precise metric for optimization, and identify what TV-side data is available (e.g., impressions, GRPs, reach, frequency).

2. Leverage external benchmarks

Use industry benchmarks for QR scan rates from similar campaigns (e.g., TV ads with QR codes) and adjust for Coinbase's brand, audience, and campaign specifics.

3. Model scan rate from TV exposure

Estimate total scans by applying a benchmark scan rate to TV impressions, then derive scan rate as scans divided by impressions; alternatively, model scans as a function of reach and frequency.

4. Validate with internal proxies

Cross-check estimates using other internal signals like app downloads, website traffic spikes during TV airings, or promo code redemptions to ensure plausibility.

5. Quantify uncertainty and communicate

Provide a range with confidence intervals based on sensitivity analysis of key assumptions, and recommend a plan to obtain better data (e.g., negotiate with agency or run a test).

Key Points to Mention

  • Triangulation: combining TV data with external benchmarks and internal proxies
  • Benchmarking: using industry QR scan rates and adjusting for context
  • Proxy metrics: app installs, site traffic, promo redemptions as indirect measures
  • Sensitivity analysis: testing how assumptions affect the estimate
  • Data negotiation: exploring ways to access agency data or set up data-sharing agreements
  • Experimental design: proposing a small-scale test to measure scan rate directly

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

Q3

Once a user lands on the page after scanning the QR code, how would you estimate the conversion rate from that landing page visit to a completed sign-up?

Product Analytics & MetricsProduct Sense & Ideation
Author's notes

Felt more comfortable here.

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AI HintsAI Generated

Suggested Approach

Start by defining the conversion event and the denominator (unique users who land on the page after scanning the QR code). Then outline how you would measure it using event tracking and funnel analysis, and discuss how to estimate it if direct data is unavailable (e.g., via proxy metrics or experimentation).

Pro tip: Emphasize the importance of segmenting by acquisition source (QR code location, campaign) and device type, as conversion rates can vary significantly and this insight can drive product improvements.

1. Define the conversion event and denominator

Clearly specify what constitutes a 'completed sign-up' (e.g., account created and verified) and the denominator: unique users who land on the page after scanning the QR code.

2. Identify data sources and tracking

Determine what event data is available (e.g., page views, sign-up completions) and ensure proper tracking is in place to attribute the landing page visit to the QR code scan.

3. Calculate conversion rate

Compute the conversion rate as the number of completed sign-ups divided by the number of unique landing page visitors, over a defined time period.

4. Estimate if data is incomplete

If direct tracking is missing, use proxy metrics (e.g., click-through rates from QR code, historical conversion rates from similar campaigns) or run a controlled experiment to estimate.

5. Validate and refine

Check for data quality issues, segment the conversion rate by relevant dimensions (e.g., device, location), and consider A/B testing to improve the rate.

Key Points to Mention

  • Define conversion event precisely (e.g., sign-up completion, email verification).
  • Use unique users as denominator to avoid double-counting.
  • Leverage event tracking (e.g., page views, sign-up events) and attribution to QR code.
  • Consider time window for conversion (e.g., same session, 7-day window).
  • Segment by acquisition source, device, and user demographics to uncover insights.
  • If data is lacking, use proxy metrics or design an experiment to estimate.

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