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Equation 20 · Part 2 · A Showdown Ladder Rating Measures the Ladder, Not the Player

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SDX1−reliability\mathrm{SD}_X\sqrt{1-\text{reliability}}
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The passage around this formula

Glickman’s RD is this same object, derived from a different starting assumption but converging on an identical use. He states the correspondence in his own words, not as an analogy this article is imposing on his work: a Glicko rating and RD together are “usually more informative to summarize a player’s strength in the form of an interval… report a 95% confidence interval. The lowest value in the interval is the player’s rating minus twice the RD, and the highest value is the player’s rating plus twice the RD” [ 3 ] . Line up the two constructions and the correspondence is not loose: SDX1−reliability\mathrm{SD}_X\sqrt{1-\text{reliability}}. This is the article’s original contribution: not the observation that a rating has…

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