Earned run average (ERA) is a statistic used in baseball to measure the effectiveness of a pitcher. It is calculated by dividing the number of earned runs allowed by a pitcher by the number of innings pitched, and then multiplying the result by nine. Earned runs are runs that are scored by the opposing team as a result of hits, walks, or errors by the pitcher. Unearned runs are runs that are scored by the opposing team as a result of errors by other fielders.
ERA is an important statistic because it provides a measure of how well a pitcher is able to prevent the opposing team from scoring runs. A low ERA indicates that a pitcher is able to keep the opposing team from scoring runs, while a high ERA indicates that a pitcher is allowing the opposing team to score runs.
