A/B Test Design: Home Page Recommendation Module
Scenario
Amazon plans to introduce a new product recommendation module on the home page and wants to evaluate its impact via online experimentation.
Task
Design an A/B test that covers:
-
Hypotheses and experiment design (test vs. control, randomization unit, targeting, and triggering).
-
Metric hierarchy: primary outcome, secondary metrics, and guardrails (with business justification).
-
Sample size and duration: how to compute, with a small numeric example; include variance-reduction options.
-
Statistical testing plan: define the p-value, how it informs decisions, and how to handle sequential looks.
-
Biases: potential sources and how you would mitigate them.
-
Limited exposure: if only 5% of users can be exposed, how to ensure adequate power.
-
Trade-off decision: treatment raises click-through-rate (CTR) but lowers average order value (AOV); how to decide whether to launch.
-
If randomization is not possible, outline a causal inference approach (e.g., difference-in-differences or propensity matching).
Include hypothesis formulation, metric hierarchy, variance reduction, sequential testing, and guardrail metrics.