Partition of a sample space
= Partition of a sample space
{title2=$\Omega=\bigsqcup_j A_j$}
A family of disjoint <events> whose union is the <sample space>. For the countable <law of total probability> and <law of total expectation>, use a finite or countably infinite family. Conditioning formulas sum only positive-probability parts, or interpret zero-probability contributions as zero without assigning a conditional expectation there.