Design an A/B Test for a New Mobile App Recommendation Algorithm
Context
A mobile app team plans to ship a new recommendation algorithm that ranks content in the app. Assume:
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We can randomize at the user level with sticky assignment.
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Traffic is sufficient to run a 50/50 A/B split after a brief ramp.
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The algorithm may change engagement and performance (e.g., latency).
Task
Describe, end-to-end, how you would design and run this A/B test:
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Experiment design
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Unit of randomization, assignment, segmentation, and ramp plan.
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Exposure definition and logging/instrumentation.
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Analysis plan and stopping rules.
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Metrics and success criteria
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Primary, secondary, and guard-rail metrics.
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How you will define success and launch criteria.
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Sample size and test duration
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How to determine required sample size and duration.
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Include formulas and a small numeric example.
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Common pitfalls and mitigations
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Discuss randomization, segmentation, statistical power, guard-rail metrics, stopping rules, and launch criteria.