Calculate variance for user retention
Last updated: November 28, 2025
Quick Overview
Given the following scenario about user conversion, calculate the the sample size needed.
Apple
November 28, 2025168
8
3,252 solved
Given the following scenario about user conversion, calculate the the sample size needed.
Analytics questions at Apple 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
- Define clear success metrics aligned with business goals
- Propose a basic experimental design with control and treatment groups
- Interpret results correctly and draw reasonable conclusions
- Identify obvious confounding variables
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 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?
- How would you handle seasonality in your experiment?
- How would you handle interference between treatment and control?
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