Compare performance of FB vs IG Stories

You are asked to compare ads performance between two placements/products (e.g., Facebook Stories vs Instagram Stories) and make a recommendation on where to allocate budget.

Task

Describe how you would conduct a fair comparison, including:

1. What primary metric you’d optimize for (and why), plus diagnostic and guardrail metrics.
2. How you’d handle attribution and cross-platform user overlap (same user on both).
3. Key confounders (audience differences, auction dynamics, creative fit, seasonality).
4. Whether you’d use observational analysis or a controlled experiment; design the experiment if applicable.
5. How you’d present results and decide budget allocation under uncertainty.

Assume you have impression-, click-, and conversion-level logs and cost data.