Rylan Schaeffer

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Probability Spaces

Parent: Probability

Definition

A probability space is a 3-tuple (\Omega, F, P) consisting of

  1. A set \(\Omega\) called the sample space i.e. the set of all possible outcomes
  2. A \(\sigma\)-algebra \(F\) on the set \(\Omega\), which informally specifies the set of all “possible” events (events are outcomes or combinations of outcomes)
  3. A probability measure \(P: F \rightarrow [0, 1]\)

The 2-tuple \((\Omega, F)\) is called a measure space.

A measurable space (also called a Borel space) is a 2-tuple consisting of

  1. A set \(X\)
  2. A A \(\sigma\)-algebra on the set \(X\)

When the 2-tuple measure space is equipped with a measure \(\mu\), becoming a 3-tuple, the measurable space becomes a measure space.