# Decision rule

Given an observable random variable X over the probability space ${\displaystyle \scriptstyle ({\mathcal {X}},\Sigma ,P_{\theta })}$, determined by a parameter θ ∈ Θ, and a set A of possible actions, a (deterministic) decision rule is a function δ : ${\displaystyle \scriptstyle {\mathcal {X}}}$→ A.