General Probability Rules

Probability Models

Vocabulary terms: Please review the definitions of these terms. They are a review of what you have learned in Algebra, Geometry and Algebra II/Trig:1. Probability2. Probability Model3. Sample Space4. Event5. Subset6. Empty Set7. Independent Events8. Disjoint Events9. Dependent Events10.Joint Events11.Tree Diagram12.With Replacement13.Without Replacement14.Complement of an Event15.Conditional Probability

6 General Probability Rules

1.) 0≤P(A)≤1 The probability that an event will occur is between 0 and 1 inclusively2.) P(S) = 1 The sum of the probabilities of all possible outcomes of an event is always 13.) P(A or B) = P(A) + P(B) - P(A∩B)

The probability that event A or event B will happen is equal to the probability that event A happens, plus the probability the event B happens minus the probability of A and B happening simultaneously.4.) P(AC) = 1-P(A) The probability of the complement of event A happening is equal to 1 minus the probability of A happening5.) P(A and B) = P(A)*P(B) if A and B are independentThe probability of event A and event B happening simultaneously is equal to the probability that event A happens multiplied by the probability that event B happens6.) P(A or B or C) = P(A) + P(B) + P(C) if A,B,C are disjoint eventsThe probability that even A, B or C occur is equal to the sum of their probabilities if the events are disjoint, if they are not disjoint, use rule #3