quantile
Returns the quantile (inverse CDF) for the given probability p.
The quantile function inverts the piecewise CDF. For probabilities up to 0.5, the result lies at or below mu; for probabilities above 0.5, the result lies above mu. Returns negative infinity for p = 0 and positive infinity for p = 1.
Return
the value x at which cdf(x) = p.
Parameters
p
the cumulative probability, must be in [0, 1].