public function was_quiz_attempt_successful( $attempt ) {

		// if the earned grade is less than or equal to zero, they failed.
		if ( $attempt->earned_marks <= 0 ) {
			return false;
		}

		// return pass or fail based on whether the required score was met.
		return ( $this->get_percentage_scored( $attempt ) >= $this->get_percentage_required( $attempt ) );
	}