rct

How to read a clinical trial result with discipline — the difference between absolute and relative risk reduction, what number-needed-to-treat captures, what confidence intervals actually mean, the hierarchy of evidence quality, and why statistical significance is not the same as clinical importance.

Most AI ROI claims are marketing, not measurement. This lesson builds a rigorous framework: how to set baselines and counterfactuals, why RCTs beat vendor case studies, the real cost components of AI deployment, and how to avoid the attribution traps that make bad investments look good on paper.

An evidence-led look at AI agents in customer support: the Brynjolfsson NBER RCT, Klarna's 2024 victory lap and 2025 walk-back, and what generalises beyond a single firm.