code: 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)));
      }
docs: {@inheritDoc}
  <p/>
  If {@code x} is more than 40 standard deviations from the mean, 0 or 1
  is returned, as in these cases the actual value is within
  {@code Double.MIN_VALUE} of 0 or 1.