A and B Test Design Questions

Designing and running A and B tests and split tests to evaluate product and feature changes. Candidates should be able to form clear null and alternative hypotheses, select appropriate primary metrics and guardrail metrics that reflect both product goals and user safety, choose randomization and assignment strategies, and calculate sample size and test duration using power analysis and minimum detectable effect reasoning. They should understand applied statistical analysis concepts including p values confidence intervals one tailed and two tailed tests sequential monitoring and stopping rules and corrections for multiple comparisons. Practical abilities include diagnosing inconclusive or noisy experiments detecting and mitigating common biases such as peeking selection bias novelty effects seasonality instrumentation errors and network interference and deciding when experiments are appropriate versus alternative evaluation methods. Senior candidates should reason about trade offs between speed and statistical rigor plan safe rollouts and ramping define rollback plans and communicate uncertainty and business implications to technical and non technical stakeholders. For developer facing products candidates should also consider constraints such as small populations cross team effects ethical concerns and special instrumentation needs.