Event and sample space

When we carry out a random experiment, the first step is to list all its possible outcomes. The set of these outcomes is called the sample space and is denoted by $\Omega$.

Definition

An event is a subset of the sample space $\Omega$, that is, of the set of all the possible outcomes of a random experiment. The probability $P(A)$ of an event is a number between $0$ and $1$ that measures “how much we expect” $A$ to occur.

A value $P(A)$ close to $0$ indicates an almost impossible event, whereas a value close to $1$ indicates an almost certain event.

Links

Topics: Probability
Concepts: Event · Probability · Sample space
Skills: Calculating probability