Design an A/B test with causal inference

You are the experimentation owner for a checkout nudge on an e-commerce platform. The experiment is randomized at the guest_id level and runs for 28 days, from 2025-09-08 through 2025-10-05. The primary success metric is a completed order within 7 days of a guest’s first exposure to the nudge. Two guardrail metrics must be monitored: bounce rate and the 95th percentile of page-load latency. Historical data show a 7-day per-guest checkout completion rate of 5%. The experiment…