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xERA and H%

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  • xERA and H%

    In another thread, I was trying to calculate Rosenthal's xERA. In doing so, I went to this page to find the formula. However, I feel like xERA should include some sort of H% variable. Rosenthal's H% in non-save situations is 57.9 (!) which I have to believe is impacting both his real-life ERA and, therefore, should be accounted for in his xERA. Is the formula on the page I linked incorrect?

    Expected earned run average(Gill and Reeve)

    (.575 x H [per 9 IP]) + (.94 x HR [per 9 IP]) + (.28 x BB [per 9 IP]) - (.01 x K [per 9 IP]) - Normalizing Factor

    "xERA represents the expected ERA of the pitcher based on a normal distribution of his statistics. It is not influenced by situation-dependent factors." xERA erases the inequity between starters' and relievers' ERA's, eliminating the effect that a pitcher's success or failure has on another pitcher's ERA.

    Similar to other gauges, the accuracy of this formula changes with the level of competition from one season to the next. The normalizing factor allows us to better approximate a pitcher's actual ERA. This value is usually somewhere around 2.77 and varies by league and year.
    If at first you don't succeed, find out if the loser gets anything.
    -Bill Lyon

  • #2
    That's the right page, but you didn't scroll down far enough. The Gill and Reeve formula is the older version, we only use that when we don't have G/L/F data available.

    Scroll down a little further and use xERA2.