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Meta·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Interviewed for a data science role at Meta, got a stats fundamentals question that felt deceptively simple but had more to it than I expected.

Questions Asked (1)

Q1

Can you explain Bayes' theorem?

A/B Testing & ExperimentationProduct Analytics & Metrics
Author's notes

Thought I had this cold.

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AI HintsAI Generated

Suggested Approach

Start with a clear, intuitive definition of Bayes' theorem, then connect it to A/B testing and product analytics at Meta. Use a concrete example, such as updating conversion rates or interpreting experiment results, to demonstrate practical understanding.

Pro tip: Emphasize how Bayes' theorem enables continuous learning from data, which is crucial for Meta's iterative product development and experimentation culture. Avoid getting bogged down in mathematical proofs; focus on application.

1. Define Bayes' Theorem

State the formula P(A|B) = P(B|A) * P(A) / P(B) and explain each term: prior, likelihood, evidence, and posterior. Keep it concise and intuitive.

2. Explain the Intuition

Describe how Bayes' theorem updates our beliefs (prior) with new evidence (likelihood) to form a revised belief (posterior). Use a simple analogy like medical testing or spam filtering.

3. Connect to A/B Testing

Discuss how Bayesian methods are used in A/B testing to compute the probability that a variant is better than control, enabling decisions without p-values. Mention advantages like interpretability and sequential testing.

4. Relate to Product Analytics

Explain how Bayes' theorem helps in modeling user behavior, such as updating conversion rates or churn probabilities as new data arrives. Highlight its role in personalization and recommendation systems.

5. Provide a Concrete Example

Walk through a simple example: Suppose a new feature has a 5% prior conversion rate; after 100 users, 10 convert. Compute the posterior probability of conversion using Bayes' theorem (with a Beta prior).

Key Points to Mention

  • Bayes' theorem formula and its components (prior, likelihood, posterior)
  • Difference between Bayesian and frequentist approaches in A/B testing
  • Use of Bayesian methods for sequential testing and early stopping
  • Application in updating user metrics like CTR or conversion rates
  • Role in personalization and recommendation algorithms at Meta
  • Importance of choosing appropriate priors and handling uncertainty

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.