Category:Union of Blocks is Set of Points

This category contains pages concerning Union of Blocks is Set of Points:

Let $\struct {X, \BB}$ be a pairwise balanced design.

That is, let $\struct {X, \BB}$ be a design, with $\size X \ge 2$, and the number of occurrences of each pair of distinct points in $\BB$ be $\lambda$ for some $\lambda > 0$ constant.

Then the set union of all the subset elements in $\BB$ is precisely $X$.