2.2.1 Which Player is better?

The winner! -- And what, if the opponent wins? -- Then the ...! -- Experience tells that almost anybody can win against any other player. But strong players win more often.

How do we account for that?

All players make bad mistakes, which inescapably end up in a defeat. Strong players make fewer mistakes. This model yields --with some assumptions and after some calculations and simplifications-- ELO's distribution formula. Because ELO's distribution gives a graphic description of the scale of rating, it will be looked at more closely, though the rating actually uses another (but very similar) distribution.