docs: public double cumulativeProbability(double x) {
          if (means != null)
              throw new IllegalStateException("Unable to sample from more than one mean");
          final double dev = x - mean;
          if (FastMath.abs(dev) > 40 * standardDeviation) {
              return dev < 0 ? 0.0d : 1.0d;
          }
          return 0.5 * (1 + Erf.erf(dev / (standardDeviation * SQRT2)));
      }