quantile
Returns the quantile (inverse CDF) for the given probability p.
Finds the value x such that cdf(x) = p using Newton's method with an initial guess based on the distribution mean.
Return
the value x at which cdf(x) = p. Returns 0.0 for p = 0 and positive infinity for p = 1.
Parameters
p
the cumulative probability, must be in [0, 1].