Statistics and Probability (Mathematics Curriculum)
Probability
What Is Probability?
Probability is a measure of how likely (how probable) an event is to happen.
Probability allows us to assign a number to the likelihood of an event: between 0 (impossible) and 1 (certain).
Dictionary Definition
The Oxford English Dictionary defines a probability as "the extent to which a particular event is likely to occur... expressed by a number between 0 and 1.
Imagine the following events.

A pig flying is impossible. It has a probability of 0. It will happen 0 times.

The probability of tossing a Head from a coin toss is ^{1}⁄_{2}.

The probability of a fully grown elephant being heavier than a man is 1. It is certain. In every case, the elephant will be heavier than the man.
These are all examples of probability.
Where Does the Word Probability Come From?
Probability comes from the Latin word 'probabilis' meaning "provable, credible".
Probability
Probability is about assigning a number to how likely an event is to happen.
In this minicurriculum, you will learn about the probability of events.
Combined Events
We can find the probability of a single event, like tossing a Heads.
What about combined events? We might want the probability of more than one event. What if this and that happen? What if that or this happen?
In this minicurriculum, you will learn about the probability of combined events.
Tree Diagrams
A tree diagram is a diagram which shows the possible outcomes of an event and their probabilities.
Each outcome is shown as a branch... which is why it is called a tree diagram.
In this minicurriculum, you will learn about tree diagrams and how to use them to calculate probabilities.