What does P(A or B) represent in probability?

The notation P(A or B) represents the probability of either event A occurring, event B occurring, or both occurring simultaneously. This is known as the union of events A and B, which is mathematically represented as P(A ∪ B).

To determine the probability of the union of two events, you can use the formula:

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

In other words, you add the probabilities of each event and then subtract the probability of their intersection (where both events occur) to avoid double counting those cases.

The concept of the union is fundamental in probability as it accommodates all possibilities where at least one of the events occurs, making it distinctively separate from the intersection or the complement of events. Understanding this helps clarify how probabilities interact in various scenarios.