Solution (source code)

= Solution

The one-observation <score function> is
$$
S_\sigma(X)=-\frac1\sigma+\frac{X^2}{\sigma^3}.
$$
Its variance, or equivalently minus the expected second derivative of the log-likelihood, is the <Fisher information matrix>[Fisher information]
$$
\boxed{I(\sigma)=\frac2{\sigma^2}}.
$$