Elo rating system

Factual Questions
1

I know there’s a formula for this and google turns up tables of stuff. where can I find the formula with no reference tables? I remember doing this dring my M:TG days…

2

never mind, I found it…

All new players start out with a base rating of 1600. The DCI uses the following equation to determine a player’s win probability in each match:

                                    1

Win Probability = --------------------------------------------------
10^((Opponent’s Rating–Player’s Rating)/400) + 1

This probability is then used to recalculate each player’s rating after the match. In the equation below, players receive 1 point if they win the match, 0 if they lose, and 0.5 for a draw. Players’ new ratings are determined as follows:

Player’s New Rating = Player’s Old Rating + (K-Value * (Scoring Points–Player’s Win Probability))

All players are rated at the beginning with the first match in which they play. Further ratings are calculated chronologically from that first match.

3

You are probably referring to the ELO expected score table, not the actual rating formula. If you want the rating formula (there are two - one for unrated/provisional players and another for previously rated palyers) you can get it here (it’s a lengthy explaination).

Googling I found that the ‘expected score table’ is the mysterious table always referred to and is a normal probability function which is used to estimate the player’s strength distribution.

4

Nitpicking here, Vriggs, but I’ve seen a lot of people make the same error and it’s a pet peeve of mine: it’s not “ELO,” like the 70’s band, but “Elo,” namely Arpad Elo, the guy who devised the system.