# 4: Sets

- Page ID
- 24834

- 4.1: Set Notation
- A set is just a collection of items and there are different ways of representing a set. We want to be able to both read the various ways and be able to write down the representation ourselves in order to best display the set. We have already seen how to represent a set on a number line, but that can be cumbersome, especially if we want to just use a keyboard.

- 4.2: The Complement of a Set
- Complements come up very often in statistics, so it is worth revisiting this, but instead of graphically we will focus on set notation. Recall that the complement of a set is everything that is not in that set. Sometimes it is much easier to find the probability of a complement than of the original set, and there is an easy relationship between the probability of an event happening and the probability of the complement of that event happening.

- 4.3: The Union and Intersection of Two Sets
- All statistics classes include questions about probabilities involving the union and intersections of sets. In English, we use the words "Or", and "And" to describe these concepts. In this section we will learn how to decipher these types of sentences and will learn about the meaning of unions and intersections.

- 4.4: Venn Diagrams
- Venn Diagrams are a simple way of visualizing how sets interact. Many times we will see a long wordy sentence that describes a numerical situation, but it is a challenge to understand. As the saying goes, "A picture is worth a thousand words." In particular a Venn Diagram describes how many elements are in each set displayed and how many elements are in their intersections and complements.