Calculate conditional probability for A/B test results

Last updated: May 28, 2026

Quick Overview

Given the following scenario about revenue per session, calculate the the sample size needed.

Capital One
Analytics & Experimentation
Data Scientist
Capital One
May 28, 2026
Data Scientist
Phone Screen
Analytics & Experimentation
Hard

2

6

4,176 solved


Given the following scenario about revenue per session, calculate the the sample size needed.

Analytics questions at Capital One evaluate your ability to define metrics, design experiments, and derive actionable insights from data. This Phone Screen question tests your end-to-end analytical thinking.

What the Interviewer Expects
  • Design complex experimentation strategies for tricky scenarios
  • Handle multi-armed bandits, switchback experiments, and quasi-experiments
  • Address long-term effects vs short-term metrics
  • Propose causal inference methods when randomization is not possible
  • Build a measurement framework that connects metrics to business value
  • Discuss organizational experimentation culture and maturity
Key Topics to Cover
Novelty and primacy effects
Guardrail metrics
A/B testing methodology
Sample size and power calculation
Simpson's paradox and ecological fallacy
How to Approach This
  1. Define success metrics carefully. A good metric is measurable, actionable, and aligned with business goals.
  2. Run experiments long enough to account for novelty effects and weekly seasonality.
  3. Use funnel analysis to identify where users drop off for maximum optimization impact.
  4. Segment results by key dimensions (platform, country, user cohort) to catch hidden patterns.
  5. Consider network effects and interference between treatment and control groups.
Possible Follow-up Questions
  • What if the experiment shows a positive short-term effect but you suspect a negative long-term impact?
  • How would you handle interference between treatment and control?
  • What would you do if a stakeholder wants to end the experiment early because initial results look good?
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