Random-orientation distribution of an apparent oblate axis ratio (source code)

= Random-orientation distribution of an apparent oblate axis ratio

For an unoriented symmetry axis chosen uniformly on the sphere, $\cos i$ is uniform on $[0,1]$. At fixed intrinsic ratio $q$, the <change-of-variables formula for a probability density> gives
$$
p(Q\mid q)=\frac{Q}{\sqrt{1-q^2}\sqrt{Q^2-q^2}},
\qquad q\leq Q\leq1.
$$