Formalism of ( Ω, F, P )
The Ω is the set of all possible outcomes. In our mathematical framework, it must be clearly defined before we can build any event structures.
A family of subsets F is a σ-algebra on Ω if it satisfies the following properties:
Ω ∈ F
The whole space is a measurable event.
A ∈ F ⇒ Ac ∈ F
If an event can occur, its non-occurrence is also measurable.
∪ Ai ∈ F
The union of any countable sequence of events is measurable.
P(A) ≥ 0 (Non-negativity)
P(Ω) = 1 (Normalization)
P(∪ Ai) = Σ P(Ai) (Countable Additivity)