Dialogue uses the Elo Rating System for sorting answers. This is a method invented by physicist Arpad Elo for calculating the relative skill levels of players in competitor-versus-competitor games such as chess. It is used as a rating system for multi-player competition in a number of video games, and major league sports including the NFL, NBA, and MLB.
The difference in the ratings between two players serves as a predictor of the outcome of a match. Two players with equal ratings who play against each other are expected to score an equal number of wins. With similar logic, a player with a higher rating than her opponent is expected to win more matches.