Range factor
Range Factor (commonly abbreviated RF) is a baseball statistic developed by Bill James. It is calculated by dividing putouts and assists by the number of innings or games played at a given defense position. The statistic is premised on the notion that the total number of outs in which a player participates is more relevant in evaluating that player's defensive play than the percentage of cleanly handled chances as calculated by the conventional statistic fielding percentage. However, some positions (especially first baseman) may have substantially more putouts because of a superior infield around them that commits fewer  errors and turns many double plays, allowing them to receive credit for more putouts. Also, catchers who have many strikeout pitchers on their team will have a high range factor, because the catcher gets the putout on a strikeout if the batter does not reach base.