What does the complement of event A consist of?

The complement of event A consists of all sample points that are not in A. This concept is fundamental in probability theory. When you have a certain event A occurring within a sample space, the complement of A, denoted usually as A', includes every outcome in the sample space that does not belong to event A.

For example, if your sample space consists of {1, 2, 3, 4, 5} and event A consists of {1, 2}, the complement of A would be {3, 4, 5}. This means that if event A occurs, then outcomes from the complement do not occur, and vice versa. Understanding complements is essential for calculating probabilities, especially when working with events that can happen or not happen in a given scenario.