In some of the videos or in videos you may find online, the terms intersection and union are used to describe compound events. While this is mathematically correct, it doesn’t help you to understand what is going on. This is further hidden when symbols are used to describe intersection and union. I often use English words to describe these events:
- the intersection of A and B, A ∩ B, is the same as A and B
- the union of A and B, A ∪ B, is the same as A or B
In other words, the English word “and” corresponds to intersection and indicates outcomes common to BOTH events. The English word “or” corresponds to union and indicates that the outcomes are in one event or in the other event.
In practice, all of these notations are in use in the real world. The key is to remember that “and” indicates what is in common and “or” indicates combining the events together.