Characteristic 2 (limited additivity). When n events A 1, …, An are incompatible with each other: P(a 1∨). . . ∪An)=P(A 1)+...+P(An)。

Real estate 3. For any event, a: p (a) = 1-p (not a).

Property 4. When events A and B satisfy that A is included in B: P(B-A)=P(B)-P(A), P(A)≤P(B).

Property 5. For any event a, P(A)≤ 1.

Real estate 6. For any two events a and b, P(B-A)=P(B)-P(AB).

Attribute 7 (addition formula). For any two events a and b, P(A∪B)= P(A)+P(B)-P(A∪B).