1) Probabilities range from 0 (no chance of the event) to 1 (the event has to happen).
For any event A, 0 ≤ P(A) ≤ 1
2) The probability of the complete sample space must equal 1.
P (sample space) = 1
3) The probability of an event not occurring is 1 minus the probability that does occur.
P(A) = 1 – P(not A)
- 4) Two events A and B are disjoint if they have no outcomes in common and can never happen together. The probability that A or B occurs is the sum of their individual
P(A or B) = “P(A U B)” = P(A) + P(B)
This is the addition rule for disjoint events.