Estimation question
Determine the right number of photos to show in Facebook's newsfeed.
- Meta
- Estimation
- Medium
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What this question tests
Tests structured estimation reasoning for a ranking and content-mix decision, balancing engagement data with content diversity.
How to approach it
- Frame this as an optimization question, not a fixed number: the right photo count depends on maximizing engagement without crowding out other valuable content types.
- Identify the tradeoff: more photos per session may raise engagement, since photo content typically drives strong interaction, but too many risks feed monotony and reduced diversity.
- Propose testing a range, for example varying photo density from 20% to 50% of feed items, via an A/B experiment rather than picking an arbitrary fixed count.
- Measure both primary and guardrail metrics: session time and engagement rate as primary, content-type diversity and creator-type representation as guardrails.
- State a directional estimate, informed by these tradeoffs, that photos likely make up somewhere around a third of feed items, pending real experimental data to confirm.
What a strong answer includes
- Reframes the question correctly as an experimental optimization rather than a number to be guessed outright.
- Names the real tradeoff, engagement versus content diversity, that determines where the right number actually lies.
- Proposes a concrete testing range instead of an arbitrary single guessed number with no path to validate it.
Common mistakes
- Giving a single confident number with no reasoning or proposed way to validate it.
- Ignoring the diversity and monotony risk of over-indexing the feed on one content type.
Likely follow-up questions
- How would you personalize this ratio per user instead of using one global number?
- How would you detect if photo density is being gamed by low-quality content creators?
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Learn the skill behind it
Chapters of the AI PM course that teach what this question tests.
- Chapter 2: Data fluency: SQL, logs, and reading the truth yourself
- Chapter 9: Prove it paid off: outcomes, economics, and pricing
- Chapter 14: Get the job: the AI PM interview loop