Editing Earned Run Average (ERA)
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In [[baseball statistics]], '''Earned Run Average''' or ERA is a measure of how many [[earned runs|earned runs]] a [[pitching (baseball)|pitcher]] can be expected to give up in nine full innings. Earned Run Average is an official [[MLB]] statistic. Earned Run Average is shown with two decimal places. | In [[baseball statistics]], '''Earned Run Average''' or ERA is a measure of how many [[earned runs|earned runs]] a [[pitching (baseball)|pitcher]] can be expected to give up in nine full innings. Earned Run Average is an official [[MLB]] statistic. Earned Run Average is shown with two decimal places. | ||
| - | Earned Run Average is calculated using this formula from rule 10.21(e) of the 2009 Official Rules<ref>{{cite-mlb | + | Earned Run Average is calculated using this formula from rule 10.21(e) of the 2009 Official Rules<ref>{{cite-web| url=http://mlb.mlb.com/mlb/downloads/y2008/official_rules/10_the_official_scorer.pdf | year=2009 | month=10 | day=21 }}</ref>: |
:<math>Earned Run Average = \frac{9*ER}{IP}</math> | :<math>Earned Run Average = \frac{9*ER}{IP}</math> | ||
A pitcher qualifies if he has pitched at least one inning for every scheduled game. | A pitcher qualifies if he has pitched at least one inning for every scheduled game. | ||
| - | Pitching championship qualification is found in rule 10.22(b) of the 2009 Official Rules<ref>{{cite-mlb | + | Pitching championship qualification is found in rule 10.22(b) of the 2009 Official Rules<ref>{{cite-web| url=http://mlb.mlb.com/mlb/downloads/y2008/official_rules/10_the_official_scorer.pdf | year=2009 | month=10 | day=21 }}</ref> |
==History== | ==History== | ||
| - | The current qualifications were put in the rule book in 1951 <ref name="Macmillan 9th edition">{{cite-book | title=The Baseball Encyclopedia 9th edition | publisher=Macmillan | city=New York | year=1993 }}))</ref>. Prior to 1951, the qualification was at | + | The current qualifications were put in the rule book in 1951 <ref name="Macmillan 9th edition">{{cite-book | title=The Baseball Encyclopedia 9th edition | publisher=Macmillan | city=New York | year=1993 }}))</ref>. Prior to 1951, the qualification was at leat 10 [[complete games|complete games]] (CG) and 100 [[innings pitched|innings pitched]] "but men who met the 1951 standard were usually recognized as leaders" with less than 10 CGs <ref name="Macmillan 9th edition" />. |
[[innings pitched|Innings pitched]] (IP) has the unique status of being the only official counting statistic that is not an integer. Instead, it is counted in thirds. Until 1978, season IPs for each pitcher were rounded off before the pitcher's ERA was calculated. This meant that a pitcher whose season IP was 1/3 (often represented as 0.1) would not be rounded down to 0 IP before calculating his ERA. If this sip of coffee pitcher had allowed 1 ER, before 1978 his ERA was infinity but starting in 1978 his ERA would be 27.00. | [[innings pitched|Innings pitched]] (IP) has the unique status of being the only official counting statistic that is not an integer. Instead, it is counted in thirds. Until 1978, season IPs for each pitcher were rounded off before the pitcher's ERA was calculated. This meant that a pitcher whose season IP was 1/3 (often represented as 0.1) would not be rounded down to 0 IP before calculating his ERA. If this sip of coffee pitcher had allowed 1 ER, before 1978 his ERA was infinity but starting in 1978 his ERA would be 27.00. | ||
In 1981 the ERA championship was ultra competitive. Using the usual rounding method, | In 1981 the ERA championship was ultra competitive. Using the usual rounding method, | ||
| - | [[Steve McCatty|Steve McCatty]]'s ERA was 2.32 ((9*48 ER)/186 IP) to nip [[Sammy Stewart|Sammy Stewart]]'s 2.33 ((9*29 ER)/112 IP). But if one didn't round the innings off, McCatty's ERA was 2.33 ((9*48 ER)/185 2/3 IP) above Sammy Stewart's 2.32 ((9*29 ER)/112 1/3 IP). McCatty was given the ERA title, but the 1982 rule book added the | + | [[Steve McCatty|Steve McCatty]]'s ERA was 2.32 ((9*48 ER)/186 IP) to nip [[Sammy Stewart|Sammy Stewart]]'s 2.33 ((9*29 ER)/112 IP). But if one didn't round the innings off, McCatty's ERA was 2.33 ((9*48 ER)/185 2/3 IP) above Sammy Stewart's 2.32 ((9*29 ER)/112 1/3 IP). McCatty was given the ERA title, but the 1982 rule book added the statemant that for the calculation of ERAs, fractional innings were not to be rounded off<ref name="Macmillan 9th edition" />. It is interesting that if you query www.mlb.com for the ERA leaders for the AL in 1981, Stewart is listed first. |
| - | <ref>{{cite-web| url=http://mlb.mlb.com/stats/historical/leaders.jsp?c_id=mlb&baseballScope=AL&statType=2&sortByStat=ERA&timeSubFrame2=1&timeFrame=1&timeSubFrame=1981 | year=2009 | month=10 | day=24 }}</ref>. Similarly, current databases store fractional IP and calculate ERA on demand using current no- | + | <ref>{{cite-web| url=http://mlb.mlb.com/stats/historical/leaders.jsp?c_id=mlb&baseballScope=AL&statType=2&sortByStat=ERA&timeSubFrame2=1&timeFrame=1&timeSubFrame=1981 | year=2009 | month=10 | day=24 }}</ref>. Similarly, current databases store fractional IP and calculate ERA on demand using current no-reounding rule, so IP and ERA from electronic source on some cases will be slightly different than IP and ERA from contemporaneous printed sources. |
<references /> | <references /> | ||
[[Category:Statistics]] | [[Category:Statistics]] | ||
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