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 decision is invariant across the whole plausible range — skip the estimate and act.
• There is no real reference class and you would invent a base rate — label it a guess, not a calibrated forecast.
• You only need a binary gate and already have a decisive observation — do not pad with ceremony.

Procedure