Definition:Power Function

Definition
Let $\theta$ be a population parameter of some population.

Let $\Omega$ be the parameter space of $\theta$. Let $\delta$ be a test procedure for hypotheses about the value of $\theta$.

Let $C$ be the critical region of $\delta$.

Let $T$ be the test statistic of $\delta$.

The power function of $\delta$, written $\map \pi {\theta_0}$, is defined by:


 * $\map \pi {\theta_0} = \map \Pr {T \in C \mid \theta = \theta_0 }$

for all $\theta_0 \in \Omega$.