LESSON: The Addition Rule

In this lesson we will be considering "compound events". Remember that a compound event is any event combining two or more simple events. 

We've worked with the Addition Rule for probability already when we learned what this symbol meant, $$\bigcup$$. It means "or". When calculating a compound probability with the $$\bigcup$$, we are essentially adding the probability of both simple probabilities together. 

If our compound events are disjoint, meaning they cannot occur together, then this calculation is simple.

If our compound events are not disjoint, then that means the events can occur together and we need to be careful how we add the probabilities together.

In the upcoming lesson video you will see an example of using the Addition Rule for a compound event that is not disjoint. We won't formalize the definition for the addition rule just yet, but it's important to understand the sprit of the rule and how to apply it to a situation intuitively.