### Wsl_F's blog

By Wsl_F, history, 23 months ago, translation, ,

Hi guys!

First of all, sorry for my poor english and short translation:)

Now everyone could access rating formulas, and there is some not obvious mathematic formulas. So, I decided to check probability formula(probability that the i-th participant has better result than the j-th participant):

There was a lot of rating codeforces rounds, so it's easy to calculate this value by existing results. I choose cf rounds №200 — №350 (separately for each division). To solve this problem I wrote java program (sources). After getting results I copy/paste it to Excel and get plots:

for first division

for second division

Looks good, but lets try found something better:)

Unfortunately this formula doesn't look scientific, so I a little bit change it:

Now, lets build plots again

for first division

for second division

Now it's closer:)

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 » 23 months ago, # |   0 Auto comment: topic has been translated by Wsl_F (original revision, translated revision, compare)
 » 23 months ago, # |   0 Auto comment: topic has been updated by Wsl_F (previous revision, new revision, compare).
 » 23 months ago, # |   +28 I believe the formula should satisfy Pi, j + Pj, i = 1.
•  » » 23 months ago, # ^ |   +47 I think it should be p(i,j) + p(j,i) + (probability of both participants having identical result) = 1 :)
•  » » » 23 months ago, # ^ |   +6 OK, that explains why the blue graph at 0 is less than 0.5.
•  » » » » 23 months ago, # ^ |   +9 Yep, the writer seems to have taken care of the mathematical details :P
•  » » » 23 months ago, # ^ |   +3 you are right:)