function quantile( p ) {
		var prob;
		var xs;

		if ( isnan( p ) || p < 0.0 || p > 1.0 ) {
			return NaN;
		}
		prob = ( p > 0.5 ) ? 1.0 - p : p;
		xs = kernelBetaincinv( v / 2.0, 0.5, 2.0 * prob, 1.0 - (2.0 * prob) );
		return sign( p - 0.5 ) * sqrt( v * xs[ 1 ] / xs[ 0 ] );
	}
Evaluates the quantile function for a Student's t distribution.

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

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