Measure Checkout Funnel Conversion Rate

Business Context

ShopNow is an e-commerce app that sells consumer electronics through web and mobile. The Head of Growth noticed that weekly purchases fell 9% after a checkout redesign, even though product page traffic was flat.

Metric Scenario

Last week, ShopNow had 1,200,000 product detail page views from 420,000 unique users, 300,000 add-to-cart events, 180,000 checkout starts, 150,000 payment submissions, and 126,000 completed orders. Leadership wants a clear definition of funnel conversion rate and a framework to measure where users are dropping off. They also want to know whether conversion should be measured at the session, user, or event level, and how to handle repeat visits, duplicate events, guest checkout, and users who convert across devices.

Requirements

1. Define the overall funnel conversion rate precisely, including numerator, denominator, and unit of analysis.
2. Define step-level conversion rates for each funnel stage and explain when each is more useful than the overall rate.
3. Explain how you would handle common edge cases: repeated events, users re-entering the funnel, cross-device identity, and canceled/refunded orders.
4. Describe how you would decompose the funnel to diagnose the 9% purchase decline.
5. Identify guardrail metrics that should be monitored alongside conversion rate.

Data Available

• page_views: user_id, anonymous_id, session_id, event_time, page_type, product_id, device_type, platform
• cart_events: user_id, anonymous_id, session_id, event_time, product_id, cart_action
• checkout_events: user_id, anonymous_id, session_id, event_time, checkout_step, payment_method, error_code
• orders: order_id, user_id, anonymous_id, session_id, order_time, order_status, gross_amount, refund_flag
• identity_map: anonymous_id, user_id, merge_time for logged-out to logged-in stitching