# Thinking Probabilistic

Use when forecasting, estimating, or sizing risk, anchor on base rates, give ranges...

- Repository: https://github.com/tjboudreaux/cc-thinking-skills (1690 stars)
- Category: Engineering
- License: MIT
- Last updated: 2026-08-07
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-probabilistic -g -a claude-code -y`
Codex: `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-probabilistic -g -a codex -y`
Cursor: `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-probabilistic -g -a cursor -y`
Gemini CLI: `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-probabilistic -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add tjboudreaux/cc-thinking-skills`

## Description

Use when forecasting, estimating, or sizing risk, anchor on base rates, give ranges, update prior→likelihood→posterior on evidence, and factor unmeasured quantities into order-of-magnitude bounds.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# 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

The rest: https://github.com/tjboudreaux/cc-thinking-skills/blob/HEAD/skills/thinking-probabilistic/SKILL.md