Probabilistic Thinking Core rule: State beliefs as numbers and ranges, not vibes. Anchor on a base rate, update with an explicit likelihood, and bound unknowns by factoring them — never invent false precision. When to Use - Timeline, effort, or outcome forecasts where the true value is uncertain. - Risk sizing for a change, migration, deploy, or launch. - Any moment you are about to state a confident single number you cannot actually know. - New evidence arrives and a prior estimate should move. When NOT to Use - The quantity is measurable or look-up-able — measure or look it up. - The decisi…