You're the analyst for a crypto exchange’s mobile onboarding funnel. KYC completion rate dropped 8% WoW during a period of high BTC volatility. Design an A/B test to improve completion without increasing fraud. Specify: a) unit of randomization (user/session/geo) and why, b) primary metric and at least two guardrails (e.g., fraud approval rate, time-to-approve, support tickets per 1k signups), c) how to neutralize exogenous market shocks (e.g., include BTC/ETH price and realized volatility as covariates with CUPED or run a Difference‑in‑Differences against a stable geo holdout), d) sample size, expected duration, and a sequential monitoring plan that controls Type I error (e.g., alpha‑spending or group‑sequential boundaries), e) country‑specific compliance step heterogeneity and app store review delays, and f) a precise pre‑registration (hypotheses, data exclusions, stopping rules, analysis plan).