experiment-designlisted

# Experiment Design ## The Law ``` AN EXPERIMENT WITHOUT A STOPPING RULE IS NOT AN EXPERIMENT — IT IS A FEATURE WAITING FOR PERMISSION. "We'll run it for a while and see" produces results that stop when the team wants them to stop — which is when they look good. Hypothesis + metric + sample size + duration + stopping rule + decision rule IS an experiment. ``` ## When to Use Trigger before: - Any A/B test on a growth surface (landing page, pricing, onboarding, email, activation flow) - Any feature gate experiment where one group sees a different experience - Any pricing or packaging test - Any content variant test that informs a product or copy decision ## When NOT to Use - Qualitative research sessions (no control group, no statistical inference — use `user-research-synthesis`) - Shadow mode deployments monitoring for regressions (not an experiment — monitoring) - Product A/B tests covered by `ab-test-design` in builder-product (use that skill for product features; use this skill for growth surfaces) ## The Six Required Elements Growth experiments share the same statistical requirements as product experiments. The difference is in the metrics and what "conversion" means. ### 1 — Hypothesis One sentence with four parts: change, metric, direction + magnitude, mechanism. ``` If we [specific change to the control experience], then [primary conversion metric] will [increase/decrease] by at least [MDE]%, because [causal mechanism — why this change affects this metric]. `