After looking at it from all sides, it seems to me that there may be a mistake in the WE calculation on FAQ. Maybe somebody can show me where I am wrong.

Let OR = Opponent's Rating and MR = My Rating.

The WE formula in FAQ is WE = 1/10^((OR - MR/400) +1)

It also gives an example where WE = **0,76** when OR - MR = 200

When I do the calculation, I get **0,32** for this sum. This means that if my rating is 200 HIGHER than my opponent, I am expected to win only one in three games, not three in four! What is my mistake??

I also find that if OR - MR = 0, i.e. *when our ratings are the SAME*, then the formula calculates a WE of 1/10, or 10%, which seems incorrect, since the intuitive answer must be 50%!

If OR - MR = - 400, then the WE is 1, i.e. I should win all games if my rating is 400 points higher. Sounds OK.

And if OR - MR = 400 (if my opponents rating is 400 points higher than mine) then the WE is 0,01,or 1%, which also makes sense, since even experts can make mistakes!

When the formula is applied in the Rating equation:

NR = OR + k(Sc - WE), then it can be seen that the WE calculation is much more lenient to the loser in a contest when you play someone stronger, than if you lose against a weaker player. I suppose that is to encourage you to play stronger players!

But there is still a problem in my mind. If there is a difference of +100 as against -100 points, the WE is 6% and 18% resp. It is difficult to understand the rationale behind this.

Can an expert perhaps explain this to me??

Muchos gracias,

CJ