In the case of making a decision between two hypotheses, "H1", absent, and "H2", present, in the event of a particular observation, "y", a classical approach is to choose "H1" when "p(H1|y) > p(H2|y)" and "H2" in the reverse case. In the event that the two "a posteriori" probabilities are equal, one might choose to default to a single choice (either always choose "H1" or always choose "H2"), or might randomly select either "H1" or "H2". The "a priori" probabilities of "H1" and "H2" can guide this choice, e.g. by always choosing the hypothesis with the higher "a priori" probability.