Solution
= Solution
Let $\pi$ be the new-treatment response probability in the trial's target population and let the fixed historical standard-of-care rate be $\pi_0$. The one-sided hypotheses are
$$
H_0:\pi\leq\pi_0,
\qquad
H_1:\pi>\pi_0.
$$
The boundary $\pi=\pi_0$ determines the type-I error because rejection probability increases with $\pi$.