The sample space is actually the set
[tex] \Omega = \{ 1,2,3,...,24,25\} [/tex]
Assuming the question is probability-based, the sigma-albegra associated is simply based on all the possible subsets of [tex] \Omega [/tex]. Finally, the probability of a certain event
[tex] P(E\subset\Omega) = \frac{n(E)}{n(\Omega)}=\frac{n(E)}{25} [/tex]
