function quantile( p ) {
		var xs;
		if ( isnan( p ) || p < 0.0 || p > 1.0 ) {
			return NaN;
		}
		xs = kernelBetaincinv( d1/2.0, d2/2.0, p, 1.0 - p );
		return d2 * xs[ 0 ] / ( d1 * xs[ 1 ] );
	}
Evaluates the quantile function for an F distribution.

@private
@param {Probability} p - input value
@returns {number} evaluated quantile function

@example
var y = quantile( 0.3 );
// returns <number>