Common baseball statistics

• batting average- ratio of base hits to at-bats (i.e. times at bat)
• runs batted in (RBI)- total number of runs a hitter generates from his at-bats, excluding runs scored due to errors by the fielding team

• Includes runs from any player, not just the batter
• Includes runs the hitter generates if he is walked, hit with the ball, or otherwise gets on base without a hit

• home run- a run scored in one at-bat

• Most commonly, the batter hits the ball out of the park, but inside-the-park home runs are also possible

• on-base percentage (OBP)- ratio of times-on-base to plate appearances; generally, it measures how often a batter reaches base

• Actual calculation is fairly complex

• slugging average- ratio of total bases (see above) to at-bats
• wins above replacement (WAR)- all-inclusive metric to “summarize a player’s total contributions to their team in one statistic.”

• Link to more details

• wins (pitching)- a starting pitcher will be credited with a win if he pitches at least 5 complete innings, his team is in the lead when he leaves the game and his team continues to maintain the lead for the rest of the game.
• loss (pitching)- any failure to achieve a win using the above criteria
• save (pitching)- awarded to pitcher when:

• He is finishing pitcher in a game won by his team
• He is not the winning pitcher
• One of the following criteria apply to him:

• He enters the game with a lead of no more than three runs and pitches for at least one inning
• He enters the game, regardless of the score, with the potential tying run either on base, at bat, or on deck
• He pitches for at least three innings

• passed ball- charged to a pitcher when he fails to hold or to control a legally pitched ball that should have been held or controlled with ordinary effort, thereby permitting a runner or runners to advance.

• Link to more details

• wild pitch- charged to a pitcher when a legally delivered ball is so high, so wide or so low that the catcher does not stop and control the ball by ordinary effort, thereby permitting a runner or runners to advance.

• Link to more details

• stolen base- when a baserunner advances by taking a base to which he isn't entitled.

• If a runner takes an extra base on a wild pitch or a passed ball, he is not awarded a stolen base. However, if he was attempting to steal as a wild pitch/passed ball was thrown, he is generally given credit for it.
• Link to more details

• earned run average (ERA)- the number of earned runs a pitcher allows per nine innings, with earned runs being any runs scored without the aid of an error or a passed ball.

• Formula:
• If a pitcher exits a game with runners on base, any earned runs scored by those runners will count against him
• Link to more details