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Roku·Data Scientist·Technical Phone Screen·Intermediate

Intermediate
Jul 2026

Summary

Roku data scientist interview with a business case question about diagnosing a profit drop at a coffee shop. Pretty classic case framing but they clearly wanted to see structured thinking, not just gut instinct.

Questions Asked (1)

Q1

You're managing a coffee shop that's been losing profit lately. Walk through how you'd systematically figure out why, including what data you'd pull, which metrics you'd calculate, and what hypotheses you'd actually test.

Root Cause AnalysisProduct Analytics & MetricsAdaptability & Ambiguity
Author's notes

I started with revenue and immediately went into ticket size and customer volume, which felt right, but I forgot to anchor the funnel properly before jumping to hypotheses.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the business context and defining the problem, then outline a structured root cause analysis: decompose profit into revenue and costs, identify key metrics, form hypotheses, and prioritize tests. Emphasize a data-driven, iterative approach that balances quick wins with deeper investigation.

Pro tip: Show that you understand the difference between correlation and causation by proposing controlled experiments (e.g., A/B tests) where possible, and always tie your analysis back to actionable business recommendations.

1. Clarify the problem and define success

Ask clarifying questions to understand the timeframe, magnitude of profit loss, and any recent changes (e.g., new competitors, menu changes). Define what 'losing profit' means (e.g., declining net margin) and set a clear goal for the analysis.

2. Decompose profit and identify key metrics

Break down profit into revenue and costs. Revenue = transactions × average order value; costs = fixed + variable. Identify metrics like daily sales, customer count, average spend, COGS, labor, rent, etc. Pull historical data to spot trends.

3. Form and prioritize hypotheses

Brainstorm potential causes: declining foot traffic, lower average spend, increased costs, operational inefficiencies, or external factors. Prioritize based on impact and ease of testing.

4. Analyze data and test hypotheses

Use data to validate or invalidate each hypothesis. For example, compare sales by daypart, product mix, customer segments; analyze cost trends; conduct cohort analysis. If possible, run experiments (e.g., promotions) to test causal relationships.

5. Synthesize findings and recommend actions

Summarize root causes, quantify their impact, and propose data-backed solutions. Prioritize actions by expected ROI and feasibility, and suggest monitoring metrics to track improvement.

Key Points to Mention

  • Profit decomposition: revenue vs. costs, and their drivers
  • Key metrics: daily sales, average order value, customer count, COGS, labor cost, gross margin
  • Data sources: POS system, loyalty program, employee schedules, supplier invoices, external data (weather, local events)
  • Hypothesis testing: A/B tests, cohort analysis, time-series analysis, segmentation
  • Prioritization frameworks: impact vs. effort, ICE score
  • Actionable recommendations: menu optimization, pricing strategies, cost reduction, marketing campaigns

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