function skewness( alpha, beta ) {
	if (
		isnan( alpha ) ||
		alpha <= 3.0 ||
		isnan( beta ) ||
		beta <= 0.0
	) {
		return NaN;
	}
	return 2.0 * ( 1.0+alpha ) / ( alpha-3.0 ) * sqrt( ( alpha-2.0 ) / alpha );
}
Returns the skewness of a Pareto (Type I) distribution.

@param {PositiveNumber} alpha - shape parameter
@param {PositiveNumber} beta - scale parameter
@returns {PositiveNumber} skewness

@example
var v = skewness( 3.5, 1.0 );
// returns ~11.784

@example
var v = skewness( 4.0, 12.0 );
// returns ~7.071

@example
var v = skewness( 8.0, 2.0 );
// returns ~3.118

@example
var v = skewness( 1.0, -0.1 );
// returns NaN

@example
var v = skewness( -0.1, 1.0 );
// returns NaN

@example
var v = skewness( 2.0, NaN );
// returns NaN

@example
var v = skewness( NaN, 2.0 );
// returns NaN