Probability

Probability is measured from 0 to 1; 0 means no event and 1 means certain event.

Probability of an event: P(event A) = # of favorable outcomes/total # of outcomes

Either of two events: P(A or B) = P(A)+P(B)-P(A and B)

Either of two mutually exclusive events: P(A or B) = P(A)+P(B)