From Veritas

**Probability** is the chanse of something happening.

**Ex 1:** The Probability of getting a 3 on a 6-dice is *1/6*.

**Ex 2:** The probablity of of raining in Sahara Desert is *very low*.

In mathematics there are four basic rules:

- For any event A, 0 ≤ P(A) ≤ 1.
- P(impossible event) = 0. Also written P(empty set) = 0 or P() = 0.
- P(sure event) = 1. Also written P(S) = 1, where S is the sample space.
- P(not A) = 1 – P(A). Also written P(complement of A) = 1 – P(A) or P(A^C) = 1 – P(A) or P(Â) = 1 - P(A)

If all outcomes of an experiment are equally likely, then:

P(A) = number of outcomes in event A / number of outcomes in the sample space