Investigate why an advertiser’s spend decreased

A video ads product has two ad formats: - **Direct ads** (optimize for in-platform actions) - **Brand ads** (user clicks the video and lands on the advertiser’s website) You notice that for a specific advertiser, **ad spend decreased materially** over the last few weeks. ### Your tasks 1. **Validate the drop is real** (not a logging/attribution/billing artifact). 2. **Quantify** the change and localize it (which product surfaces, geos, devices, formats, campaigns, days/times, etc.). 3. Propose a structured approach to **identify root cause(s)** (e.g., demand-side budget changes vs supply/auction issues vs performance/measurement changes). 4. Explain how you would distinguish between: - advertiser intentionally lowering budget/bids - platform delivering fewer impressions (supply constraint) - auction competitiveness changes - pacing/budgeting bugs - tracking/attribution changes (especially for Brand ads with offsite landing) ### Constraints to consider (discuss explicitly) - Seasonality (day-of-week, holidays) - Changes in targeting, creatives, or landing page performance - Delayed/partial labels for offsite conversions - Selection bias (survivorship of campaigns; paused campaigns) - Metric tradeoffs: revenue vs spend vs impressions vs CTR vs CVR vs CPA/ROAS ### Deliverable Walk through the analysis plan, key metrics (primary + diagnostics + guardrails), and what data cuts or experiments you would run to confirm the leading hypothesis and recommend actions.