Formulas of Probability
Distribution
Addition Rule
Key word: Or
In addition the event A or event B occurrences are equal to the probability. The formula is event A plus event B minus the probability of both A and B events.
Formulas:
P(A or B)= P(A) + P(B)-P(A and B)
or
Mutually exclusive or Disjoint:
P(A or B)= P(A) + P(B)
Multiplication Rule
Key word: And
In multiplication A and B are two
dependent events. Multiplication is
used when the probability of events A and B
occurs are equal. The is event A times event B occurs, which A is given.
P(A and B) = P(A) P(B|A)
Subtraction Rule
Key word: At least one
The subtraction rule also known
as the complement rule is when an
event is NOT occurring.
P(A) = 1 - P(A')