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Meta·Data Scientist·Technical Phone Screen·Senior

Senior
Jul 2023Remote

Summary

Meta DS interview with a SQL question that sounds straightforward until you actually have to define what you're measuring. The open-ended metric design part is where it gets interesting.

Questions Asked (1)

Q1

Given a table of historical shop visibility actions, write a SQL query that computes a metric comparing how likely older users versus newer users are to set their shop profile to invisible. Justify your metric choice.

Product Analytics & MetricsData Modeling
Author's notes

The SQL itself isn't the hard part.

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AI HintsAI Generated

Suggested Approach

First, clarify the table schema and define 'older' vs 'newer' users based on account age or tenure. Then, choose a metric like the odds ratio or risk ratio of setting shop invisible, computed with SQL using conditional aggregation and window functions if needed. Finally, justify why this metric is appropriate for comparing two groups in a product analytics context.

Pro tip: Mention that you would check for confounding variables like user activity level or shop type, and consider using a logistic regression model for a more robust comparison if the data allows.

1. Understand the data and define groups

Inspect the table schema to identify columns for user ID, action timestamp, action type (visible/invisible), and user signup date. Define 'older' and 'newer' users based on a threshold of account age (e.g., median tenure).

2. Choose an appropriate metric

Select a metric that compares the likelihood of the action between groups, such as the odds ratio or risk ratio. Consider if you need to account for time or repeated actions per user.

3. Write the SQL query

Use conditional aggregation to compute the number of users who set shop invisible and total users in each group. Then calculate the metric, possibly using subqueries or CTEs for clarity.

4. Justify the metric choice

Explain why the chosen metric is suitable: e.g., odds ratio is interpretable, handles unbalanced group sizes, and is standard in product analytics for comparing binary outcomes.

5. Consider edge cases and validation

Discuss handling users with multiple actions (e.g., take the latest action or first action), missing data, and potential confounders. Suggest validating results with a statistical test or model.

Key Points to Mention

  • Define 'older' vs 'newer' users clearly, possibly using account age or tenure.
  • Choose a metric like odds ratio or risk ratio, and explain its interpretability.
  • Use SQL features like CTEs, window functions, or conditional aggregation for efficient computation.
  • Address repeated actions per user by selecting a representative action (e.g., first or last).
  • Mention potential confounders (e.g., user activity, shop category) and how to control for them.
  • Justify the metric's suitability for product analytics and decision-making.

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