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Equation 20 · Part 1 · A Showdown Ladder Rating Measures the Ladder, Not the Player

Symbol X

SDX1−reliability\mathrm{SD}_X\sqrt{1-\text{reliability}}
XX

What this part means

X is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Its job in the formula

X is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

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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