Calculate variance for coin flips
Last updated: September 29, 2025
Quick Overview
Given the following scenario about revenue per session, calculate the the sample size needed.
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September 29, 20257
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Given the following scenario about revenue per session, calculate the the sample size needed.
Analytics questions at Zoom evaluate your ability to define metrics, design experiments, and derive actionable insights from data. This Onsite 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
- What would you do if a stakeholder wants to end the experiment early because initial results look good?
- How would you handle an experiment where the control and treatment groups are different sizes?
- What if you discover a bug in the logging during the experiment?
- What if the experiment shows a positive short-term effect but you suspect a negative long-term impact?
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Defining the Analysis Framework
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Analysis Approach
**Exploratory Analysis**: Start with aggregate trends, then segment by key dimensions (platform, country, user cohort, channel). Look for heterogeneou...
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