pub fn beta_quantile(p: f64, a: f64, b: f64) -> f64Expand description
Quantile (inverse CDF) of a Beta distribution with shape parameters a > 0
and b > 0 at probability p ∈ (0, 1): the value x ∈ [0, 1] with
I_x(a, b) = p, where I is the regularized incomplete beta (the Beta CDF).
p ≤ 0 maps to the 0 support floor and p ≥ 1 to the 1 support ceiling;
a non-finite or non-positive shape yields NaN. Built on the AS 64/109
inverse-incomplete-beta routine.
This is the bounded-support analogue of gamma_quantile: a Beta response
(a proportion modelled by the Beta family) is skewed toward whichever edge
its mean is near, so a symmetric μ ± z·σ predictive band mis-covers both
tails even when its width is correct. Equal-tailed Beta quantiles place the
right mass in each tail (#1194).