Capital One·Data Scientist·Technical Phone Screen·Senior

Senior

Jun 2026

Summary

Capital One data scientist interview with a meaty case question that blended experiment design, business judgment, and break-even math all in one prompt. Felt more like a consulting case than a typical DS screen.

Questions Asked (1)

A restaurant is considering joining a coupon program. What concrete factors and metrics would you evaluate before signing on, how would you design an experiment to estimate incremental profit impact, and what is the minimum share of coupon tables that must be truly incremental for the program to break even, given specific baseline and observed numbers?

A/B Testing & ExperimentationPricing & MonetizationProduct Analytics & Metrics

Author's notes

This was a three-part monster and I didn't pace myself well.

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AI HintsAI Generated

Suggested Approach

Start by outlining the key business and financial factors to evaluate, such as coupon discount, redemption rate, and baseline margins. Then describe a rigorous experiment design, like a randomized controlled trial or geo-test, to measure incremental profit. Finally, calculate the break-even incremental share using the provided numbers, ensuring to account for cannibalization and costs.

Pro tip: Emphasize that correlation does not imply causation—without a proper control group, coupon users may be self-selected and not incremental. Also, consider the long-term impact on customer behavior and brand perception, not just short-term profit.

1. Identify Key Factors and Metrics

List concrete factors like coupon discount, redemption rate, average check size, baseline profit margin, and fixed fees. Define metrics such as incremental revenue, incremental profit, and coupon ROI.

2. Design an Incrementality Experiment

Propose a randomized controlled trial where some locations or time periods offer the coupon and others do not. Use difference-in-differences or A/B testing to isolate the coupon's causal effect on profit.

3. Calculate Break-Even Incremental Share

Using baseline and observed numbers, compute the minimum share of coupon tables that must be truly incremental for the program to break even. Set incremental profit = 0 and solve for the share.

4. Consider Additional Risks and Long-Term Effects

Discuss potential cannibalization, dilution of brand equity, and changes in customer lifetime value. Recommend monitoring these over time.

Key Points to Mention

Incremental profit = (Incremental revenue from coupon users) - (Coupon discount cost + fixed fees + variable costs)
Break-even incremental share = (Cost per coupon table) / (Profit per incremental table)
Use of control groups to measure true incrementality and avoid selection bias
Consideration of cannibalization: coupon users who would have visited anyway
Importance of segmenting by customer type (new vs. existing) and time of day
Long-term impact on customer retention and average order value

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