Event Space/Examples/Arbitrary Event Space on 6-Sided Die
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Example of Event Space
Let $\EE$ be the experiment of throwing a standard $6$-sided die.
The sample space of $\EE$ is $\Omega = \set {1, 2, 3, 4, 5, 6}$.
Let $\FF$ be the arbitrary set of subsets of $\Omega$ defined as:
- $\FF = \set {\O, \set {1, 2}, \set {3, 4}, \set {5, 6}, \set {1, 2, 3, 4}, \set {3, 4, 5, 6}, \set {1, 2, 5, 6}, \Omega}$
Then $E$ is an event space of $\EE$.
Proof
It is specified that $\O \in \FF$.
Thus axiom $(\text {ES} 1)$ is fulfilled.
$\Box$
It is specified that $\Omega \in \FF$.
Thus axiom $(\text {ES} 2)$ is fulfilled.
$\Box$
We investigate the unions of elements of $\Omega$.
From Union with Superset is Superset, it is unnecessary to investigate the union of any element of $\Omega$ with a subset of it.
We continue:
\(\ds \set {1, 2} \cup \set {3, 4}\) | \(=\) | \(\ds \set {1, 2, 3, 4}\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {1, 2} \cup \set {5, 6}\) | \(=\) | \(\ds \set {1, 2, 5, 6}\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {3, 4} \cup \set {5, 6}\) | \(=\) | \(\ds \set {3, 4, 5, 6}\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {1, 2} \cup \set {3, 4} \cup \set {5, 6}\) | \(=\) | \(\ds \set {1, 2, 3, 4, 5, 6} = \Omega\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {1, 2, 3, 4} \cup \set {1, 2, 5, 6}\) | \(=\) | \(\ds \set {1, 2, 3, 4, 5, 6} = \Omega\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {1, 2, 3, 4} \cup \set {3, 4, 5, 6}\) | \(=\) | \(\ds \set {1, 2, 3, 4, 5, 6} = \Omega\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {1, 2, 5, 6} \cup \set {3, 4, 5, 6}\) | \(=\) | \(\ds \set {1, 2, 3, 4, 5, 6} = \Omega\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {1, 2} \cup \set {3, 4, 5, 6}\) | \(=\) | \(\ds \set {1, 2, 3, 4, 5, 6} = \Omega\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {3, 4} \cup \set {1, 2, 5, 6}\) | \(=\) | \(\ds \set {1, 2, 3, 4, 5, 6} = \Omega\) | \(\ds \in \Omega\) | |||||||||||
\(\ds \set {5, 6} \cup \set {1, 2, 3, 4}\) | \(=\) | \(\ds \set {1, 2, 3, 4, 5, 6} = \Omega\) | \(\ds \in \Omega\) |
$\Box$
All the event space axioms are seen to be fulfilled by $\powerset \Omega$.
Hence the result.
$\blacksquare$
Sources
- 1986: Geoffrey Grimmett and Dominic Welsh: Probability: An Introduction ... (previous) ... (next): $1$: Events and probabilities: $1.2$: Outcomes and events: Example $6$