Variance bound for a weakly self-bounding function (source code)

= Variance bound for a weakly self-bounding function

For a weakly self-bounding function $Z=f(X_1,\ldots,X_n)$ of <independent random variables>, the coordinatewise variance inequality gives
$$
\operatorname{Var}(Z)\leq\mathbb E\sum_i(Z-Z_i)^2\leq\mathbb EZ,
$$
where $Z_i=f_i(X^{(i)})$.