Probability Rules/Non-Disjoint Events and Conditional Probability

This packet has two videos. The first video shows you the definitions for non-disjoint events and conditional probability, as well as the probability rules for each. The second video shows an example for calculating both non-disjoint event probabilities and conditional probabilities. Some terms that may be new are:

• The General Addition Rule
• Conditional Probability
• The General Multiplication Rule
• With Replacement versus Without Replacement

Here are some basic definitions for this packet:

General Addition Rule: The probability of one or both of a pair of events happening is equal to the sum of their individual probabilities minus the probability of both of them happening. This applies to events that are not disjoint. 

Formula: P(A or B) = P(A) + P(B) - P(A and B)

Conditional probability: The probability of an event A happening given the fact that event B already has happened is equal to the probability of both A and B happening divided by the probability of B happening.

Formula: P(A|B) = P(A and B)/P(B)