code: function calculateNormalZProbability(z) {
      if (z == 0.0) {
          var x = 0.0;
      }
      else {
          var y = 0.5 * Math.abs(z);
  
          // Here comes the magic.
  
          if (y >= Z_MAX * 0.5) {
              x = 1.0;
          }
          else if (y < 1.0) {
              var w = y * y;
  
              x = 0.000124818987 * w -0.001075204047;
              x *= w +0.005198775019;
              x *= w -0.019198292004;
              x *= w +0.059054035642;
              x *= w -0.151968751364;
              x *= w +0.319152932694;
              x *= w -0.531923007300;
              x *= w +0.797884560593;
              x *= y * 2.0;
          }
          else {
              y -= 2.0;
  
              x = -0.000045255659 * y +0.000152529290;
              x *= y -0.000019538132;
              x *= y -0.000676904986;
              x *= y +0.001390604284;
              x *= y -0.000794620820;
              x *= y -0.002034254874;
              x *= y +0.006549791214;
              x *= y -0.010557625006;
              x *= y -0.010557625006;
              x *= y +0.011630447319;
              x *= y -0.009279453341;
              x *= y +0.005353579108;
              x *= y -0.002141268741;
              x *= y +0.000535310849;
              x *= y +0.999936657524;
          }
      }
  
      return z > 0.0 ? (x + 1.0) * 0.5 : (1.0 - x) * 0.5;
  }
docs: Calculates the probability for the normal z.
  
  @param {Number} z
  @return {Number}