function quantile( p ) {
		if ( isnan( p ) || p < 0.0 || p > 1.0 ) {
			return NaN;
		}
		return sqrt( -2.0 * s2 * log1p( -p ) );
	}
Evaluates the quantile function for a Rayleigh distribution.

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

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