Calculate conditional probability for A/B test results

Last updated: November 19, 2025

Quick Overview

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

NVIDIA

Analytics & Experimentation

Data Scientist

NVIDIA

November 19, 2025

Data Scientist

Phone Screen

Analytics & Experimentation

Medium

1,090 solved

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

Analytics questions at NVIDIA 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 a rigorous experiment with proper randomization and sample size calculation
Define primary and guardrail metrics with clear rationale
Address novelty effects, network effects, and interference
Segment results appropriately and identify heterogeneous treatment effects
Propose follow-up analyses when results are ambiguous

Key Topics to Cover

Long-term vs short-term metrics

Guardrail metrics

Metric definition and success criteria

A/B testing methodology

How to Approach This

Define success metrics carefully. A good metric is measurable, actionable, and aligned with business goals.
Run experiments long enough to account for novelty effects and weekly seasonality.
Use funnel analysis to identify where users drop off for maximum optimization impact.
Segment results by key dimensions (platform, country, user cohort) to catch hidden patterns.
Consider network effects and interference between treatment and control groups.

Possible Follow-up Questions

How would you handle an experiment where the control and treatment groups are different sizes?
What would you do if a stakeholder wants to end the experiment early because initial results look good?
How would you handle seasonality in your experiment?

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Sample Answer

Problem Setup

The analytical question involves determining the sample size necessary to conduct an A/B test that measures the impact of a new feature on revenue per session for NVIDIA. To set up the problem, we nee...

Methodology

To calculate the sample size for the A/B test, we will use the formula for sample size in comparing two means:

[ n = \left( \frac{(Z_{\alpha/2} + Z_{\beta})^2 \cdot $\sigma_1^2 + \sigma_2^2$ }{(\mu_1...

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