Figure 1.

Sample probability mass diagrams, which use length to represent the probability mass of each joint event from $\mathcal{T}\times \mathcal{S}$. (Left) the joint distribution $P(S,T)$; (Middle) The occurrence of the event $s^1$ leads to exclusions of the complementary event ${s^1}^{\mathsf{c}}$ which consists of two elementary event, i.e., ${s^1}^{\mathsf{c}}=\{s^2,s^3\}$. This leaves the probability mass $P(s^1,T)$ remaining. The exclusion of the probability mass $p({s^1}^{\mathsf{c}},t^1)$ was misinformative since the event $t^1$ did occur. By convention, misinformative exclusions will be indicated with diagonal hatching. On the other hand, the exclusion of the probability mass $p({t^1}^{\mathsf{c}},{s^1}^{\mathsf{c}})$ was informative since the complementary event ${t^1}^{\mathsf{c}}$ did not occur. By convention, informative exclusions will be indicated with horizontal or vertical hatching; (Right) this remaining probability mass can be normalised yielding the conditional distribution $P(T|s^1)$.