A random variable is a variable whose value depends on the outcome of a random event.

The range of values that a random variable can take is called a sample space.

A discrete variable can only take specific numerical values, and a continuous variable can take any numerical value in a range.

A probability distribution describes the probably of any outcome in the sample space.

Discrete random variables

The probability distribution of a discrete random variable can be described in the following ways:

Using a probability mass function

Using a table

Using a diagram