docs: function normcdf(x) {
    var a1 = 0.398942280444;
    var a2 = 0.399903438504;
    var a3 = 5.75885480458;
    var a4 = 29.8213557808;
    var a5 = 2.62433121679;
    var a6 = 48.6959930692;
    var a7 = 5.92885724438;
    var b0 = 0.398942280385;
    var b1 = 3.8052E-08;
    var b2 = 1.00000615302;
    var b3 = 3.98064794E-04;
    var b4 = 1.98615381364;
    var b5 = 0.151679116635;
    var b6 = 5.29330324926;
    var b7 = 4.8385912808;
    var b8 = 15.1508972451;
    var b9 = 0.742380924027;
    var b10 = 30.789933034;
    var b11 = 3.99019417011;
    var q;
    var y;
    var absx = Math.abs(x);
  
    if (absx <= 1.28) {
      y = 0.5 * x * x;
      q = 0.5 - absx * (a1 -
        a2 * y / (y + a3 -
        a4 / (y + a5 +
        a6 / (y + a7))));
    } else if (absx <= 12.7) {
      y = 0.5 * x * x;
      q = Math.exp(-y) * b0 / (absx - b1
        + b2 / (absx + b3
        + b4 / (absx - b5
        + b6 / (absx + b7
        - b8 / (absx + b9
        + b10 / (absx + b11))))));
    } else {
      q = 0.0;
    }
  
    if (x < 0.0)
    {
      return q;
    }
    return 1.0 - q;
  }