# Probability.

Four foundational chapters — PR001 through PR004 — form a connected sequence with twelve interactive steps each.

Continue to binomial path counting, Gaussian distributions, uncertainty, likelihood and Bayesian updating.

Canonical page: https://21ifm.com/probability

## Explore

- [Complement and addition rules](https://21ifm.com/probability/complements-addition)
- [Multiplication and independence](https://21ifm.com/probability/multiplication-independence)
- [Counting, permutations and combinations](https://21ifm.com/probability/permutations-combinations)
- [Conditional and total probability](https://21ifm.com/probability/conditional-total-probability)