Calculate conditional probability for coin flips

Last updated: December 5, 2025

Quick Overview

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

Jump Trading

Analytics & Experimentation

Data Scientist

Jump Trading

December 5, 2025

Data Scientist

Phone Screen

Analytics & Experimentation

Medium

2,303 solved

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

Analytics questions at Jump Trading 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

Guardrail metrics

Network effects and interference

Novelty and primacy effects

Segmentation and heterogeneous effects

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

What if the experiment shows a positive short-term effect but you suspect a negative long-term impact?
What if you discover a bug in the logging during the experiment?
How would you handle seasonality in your experiment?

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Sample Answer

Problem Setup

To calculate the sample size needed for our experiment regarding revenue per session based on coin flips, we need to frame our analytical question as follows: "What is the effect of a coin flip (as a ...

Methodology

We will use the formula for sample size calculation for comparing two means (treatment vs control). The formula is:

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

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