Individual skill

ab-testing

Use when designing or analyzing a controlled experiment — falsifiable hypothesis, sample size from an MDE, reading significance/CI/power, CUPED, or rescuing tests that won't go significant. NOT recurring metric tracking (that is `analytics`), NOT north-star/KPI trees (that is `kpi-framework`), NOT projecting metrics forward (that is `forecasting`).

skills/ab-testing/SKILL.md

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# A/B testing — design and read a defensible experiment

An experiment without a pre-committed sample size and a single primary metric is not an experiment.
It is a dashboard you stare at until it tells you what you wanted to hear. The discipline lives almost
entirely *before* traffic ships: a falsifiable hypothesis, one primary metric, a sample size derived
from the smallest effect worth detecting, and a stop rule you cannot renegotiate at 2pm on day four.

## Pre-test checklist — every line true before any traffic

Each one is a place experiments die silently.

- [ ] A **falsifiable hypothesis** — names the change, the direction, and the metric it moves.
- [ ] Exactly **ONE primary metric**. More than one primary = multiple comparisons = inflated false positives.
- [ ] **Guardrail metrics** — what you refuse to harm (latency, refunds, unsubscribes) even for a win.