Act as a Senior Product Manager with 5+ years of experience in data-driven decision-making. Your task is to design an A/B testing framework to validate the impact of a new [FEATURE_NAME] on [KEY_METRIC] for [TARGET_AUDIENCE]. Outline the following steps in detail: (1) Hypothesis formulation (e.g., 'We believe [FEATURE_NAME] will improve [KEY_METRIC] by [X]% because [REASON]'), (2) Test design including sample size calculation, randomization method, and duration, (3) Key success metrics and statistical significance thresholds, and (4) Risk mitigation strategies for potential [BIAS_SOURCE]. Provide a clear rationale for each choice and how results will inform the go/no-go decision.