Diagnose a YouTube Launch That Lifted Mobile Views 10% but Cut Desktop Comments 20%
Company: Meta
Role: Product Manager
Category: Analytics & Experimentation
Difficulty: medium
Interview Round: Other
You are a product manager at YouTube, and your team has just launched a new feature. Which feature it is does not matter for this exercise. Since the launch, the number of video views on mobile has risen by 10%, and the number of comments posted under videos on desktop has fallen by 20%. What would you do?
```hint One shift or two?
Before deciding whether the launch helped or hurt, ask whether these two numbers could describe a single change in how people use YouTube, and what data would tell you.
```
### Clarifying Questions
- Are both figures totals across all videos and users, and are they compared with the period before launch or with a control group that did not get the feature?
- Did the feature ship on mobile, desktop or both, and to all users at once or as a gradual rollout?
- What happened to the numbers the prompt leaves out: desktop views, mobile comments, total comments and watch time?
- Which metric was this launch meant to move?
### What a Strong Answer Covers
- Checking that both movements are real and caused by the launch before interpreting them.
- Filling in the missing cells (views and comments on each platform, totals and per-user rates) to see whether behavior moved between devices or actually changed.
- Hypotheses that connect the rise in mobile views with the fall in desktop comments, each paired with the data that would test it.
- Weighing a view against a comment in terms of value to viewers, creators and YouTube, leading to a clear keep, iterate or roll back decision.
- Metrics and guardrails for monitoring the feature after the decision.
### Follow-up Questions
- The analysis shows that total comments across both platforms are down, not just shifted between devices. Does that change your decision?
- Creators report that their comment sections have gone quiet since the launch. How do you respond, and what would you measure?
- How would you design the launch experiment next time so that cross-device effects like this one are caught before full rollout?
Overview: A product analytics interview question set at YouTube: after a new feature launch, mobile video views rise 10% while desktop comments fall 20%. It tests validating metric movements, linking changes across devices, forming testable hypotheses, and deciding whether to keep, iterate on or roll back the feature.