function skewness( n, p ) {
	if (
		isnan( n ) ||
		isnan( p ) ||
		p < 0.0 ||
		p > 1.0 ||
		!isNonNegativeInteger( n ) ||
		n === PINF
	) {
		return NaN;
	}
	return ( 1.0 - ( 2.0*p ) ) / sqrt( n * p * ( 1.0-p ) );
}
Returns the skewness of a binomial distribution.

@param {NonNegativeInteger} n - number of trials
@param {Probability} p - success probability
@returns {number} skewness

@example
var v = skewness( 100, 0.1 );
// returns ~0.267

@example
var v = skewness( 20, 0.5 );
// returns 0.0

@example
var v = skewness( 10.3, 0.5 );
// returns NaN

@example
var v = skewness( 20, 1.1 );
// returns NaN

@example
var v = skewness( 20, NaN );
// returns NaN