function factory( n ) {
	var mlim;
	var pui;

	if ( !isPositiveInteger( n ) || !isfinite( n ) ) {
		return constantFunction( NaN );
	}
	pui = exp( -n * LN2 );
	mlim = n * ( n + 1 ) / 2;
	return cdf;

	/**
	* Evaluates the cumulative distribution function (CDF) for the distribution of the Wilcoxon signed rank test statistic.
	*
	* @private
	* @param {number} x - input value
	* @returns {Probability} evaluated CDF
	*
	* @example
	* var y = cdf( 2 );
	* // returns <number>
	*/
	function cdf( x ) {
		var i;
		var p;
		if ( isnan( x ) ) {
			return NaN;
		}
		if ( x < 0.0 ) {
			return 0.0;
		}
		x = round( x );
		if ( x >= mlim ) {
			return 1.0;
		}
		p = 0;
		for ( i = 0; i <= x; i++ ) {
			p += weights( i, n ) * pui;
		}
		return p;
	}
}
Returns a function for evaluating the cumulative distribution function (CDF) for the distribution of the Wilcoxon signed rank test statistic with `n` observations.

@param {PositiveInteger} n - number of observations
@returns {Function} CDF

@example
var cdf = factory( 8 );
var y = cdf( 3.9 );
// returns ~0.027

y = cdf( 17.0 );
// returns ~0.473