function apnorm( z ) {
	var expntl;
	var zabs;
	var pdf;
	var p;
	var q;

	zabs = abs( z );
	if ( zabs > 37.0 ) {
		if ( z > 0.0 ) {
			p = 1.0;
		} else {
			p = 0.0;
		}
	} else {
		// Case: |z| >= 37
		expntl = exp( -0.5 * zabs * zabs );
		pdf = expntl / SQRT_TWO_PI;
		if ( zabs < CUTOFF ) {
			p = expntl * ((((((p6 * zabs + p5) * zabs + p4) * zabs + p3) * zabs + p2) * zabs + p1) * zabs + p0) /
				(((((((q7 * zabs + q6) * zabs + q5) * zabs + q4) * zabs + q3) * zabs + q2) * zabs + q1) * zabs + q0);
		}
		else {
			p = pdf / (zabs + 1.0 / (zabs + 2.0 / (zabs + 3.0 / (zabs + 4.0 / (zabs + 0.65)))));
		}
		if ( z >= 0.0 ) {
			q = p;
			p = 1.0 - q;
		}
	}
	return p;
}
Evaluates the CDF of the standard normal distribution.

@private
@param {number} z - standard deviation from the mean
@returns {number} evaluated CDF