code: public static double quantile(double x, double mu, double sigma) {
      return FastMath.exp(mu + sigma * NormalDistribution.standardNormalQuantile(x));
    }
docs: Inverse cumulative probability density function (probit) of a normal
  distribution.
  
  @param x value to evaluate probit function at
  @param mu Mean value
  @param sigma Standard deviation.
  @return The probit of the given normal distribution at x.