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Equation 7 · Part 4 · A Showdown Ladder Rating Measures the Ladder, Not the Player

addition

RDnew period=RDold2+c2\mathrm{RD}_{\text{new period}} = \sqrt{\mathrm{RD}_{\text{old}}^2 + c^2}
addition

What this part means

Add the term after the plus sign to the term or group before it.

Its job in the formula

Add the term after the plus sign to the term or group before it.

The passage around this formula

where d2d^2 is a variance term built from the same g(RDj\mathrm{RD}_j) and expected-score factors, sjs_j ∈\in \{0, 0.5, 1\} is the outcome of game j , and between rating periods the deviation itself grows on a fixed schedule, RDnew period\mathrm{RD}_{\text{new period}} = RDold2+c2\sqrt{\mathrm{RD}_{\text{old}}^2 + c^2} , clamped to Showdown’s own configured ceiling of 130 rather than Glickman’s generic default ceiling of 350 [ 2 , 3 ] . Substitute Showdown’s published c = 6.6775026092 and the schedule is fully determined: it is not a metaphorical “uncertainty,” it is a specific number computed the same way every 24 hours for every account on the ladder. A brand-new Showdown account starts at RD = 130 — already at the…

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