Solution
= Solution
The <marginal likelihood> integrates the <likelihood function> against the <prior density>:
$$
\boxed{Z:=p(\mathcal D)=\int_{\mathbb R^d}p(\mathcal D\mid\theta)p(\theta)\,d\theta}.
$$
It is the normalizing constant in <Bayes' theorem>. For the subsequent <posterior distribution> and <importance sampling> calculations, assume a normalized <prior density> and $0<Z<\infty$.