code: function pnorm(qn) {
          var b = [1.570796288, 0.03706987906, -0.8364353589e-3,
                  -0.2250947176e-3, 0.6841218299e-5, 0.5824238515e-5,
                  -0.104527497e-5, 0.8360937017e-7, -0.3231081277e-8,
                  0.3657763036e-10, 0.6936233982e-12],
              w1 = qn,
              w3 = -Math.log(4.0 * w1 * (1.0 - w1)),
              i = 1;
  
          if (qn < 0.0 || qn > 1.0) { return 0.0; }
          if (qn === 0.5) { return 0.0; }
          if (qn > 0.5) { w1 = 1.0 - w1; }
  
          w1 = b[0];
          for (i; i < 11; i++) {
              w1 += b[i] * Math.pow(w3, i);
          }
  
          if (qn > 0.5) { return Math.sqrt(w1 * w3); }
  
          return -Math.sqrt(w1 * w3);
      }
docs: inverse of normal distribution ([2]) Pr( (-\infty, x] ) = qn -> x