Calculate conditional probability for user retention
Last updated: April 29, 2026
Quick Overview
Given the following scenario about revenue per session, calculate the the sample size needed.
Compass
April 29, 202616
14
2,162 solved
Given the following scenario about revenue per session, calculate the the sample size needed.
Analytics questions at Compass 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
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 interference between treatment and control?
- 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?
- What if you discover a bug in the logging during the experiment?
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Browse Analytics QuestionsSample Answer
Problem Setup
To calculate the conditional probability for user retention based on revenue per session, we need to define the analytical question: **What is the probability that a user retains after a session that ...
Methodology
We will conduct a hypothesis test to determine the conditional probability of retention based on session revenue. The steps include:
- Define the Success Criteria: Retention is defined as a u...
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