Asri-unix.1106
net.chess
utzoo!decvax!ucbvax!C70:sri-unix!mclure@SRI-UNIX
Fri Mar 26 15:13:32 1982
Elo provisional formula
I was just glancing through the Elo book and noticed a strange formula
used for provisional ratings.

		    400 ( W - L )
	R  = R   +  -------------
	 p    c          N

Where
	R   = provisional rating
	 p
	R   = average of competition ratings
	 c
	W   = wins (draws count 1/2)
	L   = losses (draws count 1/2)
	N   = number of games played

This means that if you are unrated and play the following games


	Opponent rating	   your score
A)	1200		   1
	1200		   1
	1300		   1
	1350		   0
	1400		   0

B)	1200		   1
	1200		   1
	1300		   1
	2200		   0
	2200		   0

something odd occurs.  The only difference between batch A and batch
B is that in B your two losses have been to masters rather than 1350
and 1400 players.  However the difference between losing to 1350 and
1400 and losing to two masters is great.  The resulting ratings are
1370 and 1700 respectively.  A 330 point difference.

Naturally they will start you out at the lowest class E/unrated and
you won't have the advantage of playing against masters. But if you
are in league play, as we are in the Bay Area among certain companies,
it *really* pays to play against highly rated players while you
are in your provisional period (20 or 24 games I think).

This seems very peculiar.