Author: Robert Hyatt
Date: 08:07:55 12/03/00
Go up one level in this thread
On December 02, 2000 at 23:01:21, Jeff Lischer wrote: >On December 01, 2000 at 23:23:35, Robert Hyatt wrote: > >>On December 01, 2000 at 11:09:19, Jeroen van Dorp wrote: >> >>>On November 30, 2000 at 19:53:55, Terry Ripple wrote: >>> >>>>If a Player is rated 2500 FIDE, then what would be his aproximate USCF rating? >>>> >>>>Thanks in advance for your information! >>>> >>>>Regards,Terry >>> >>> >>>USCF = (ELO * 0.895) + 367. >>>ELO = (USCF -367)/0.895 >>> >>> >>> >>>so 2500 FIDE = 2383 >>> >>> >>>Jeroen ;-} >> >> >>That's way off. Ken Sloan did a careful comparison a few years ago, and found >>that at the 2500+ level, USCF was about 35 points higher IIRC. Not over a >>hundred as the above formula predicts. IN fact, the conversion formula would >>be a non-linear equation as the difference varies depending on the rating... >>More at lower levels, less at the top. > >Section 28D1 in the 4th Edition of the USCF Official rules of chess gives the >following conversions: > >(1) USCF = FIDE + 50 >(2) USCF = 0.895*FIDE + 367 > >It goes on to say: > >"Formula (1) represents an average conversion. This means that 50% of the time >the FIDE-rated player will be stronger than his or her converted USCF rating >would indicate. By using formula (2), on the other hand, a tournament director >ensures that the FIDE-rated player will be stronger than his or her converted >USCF rating only 10% of the time, thus providing a greater degree of protection >for the players with established USCF ratings." I have no idea how recently that formula was crafted... The point is that Ken Sloan took the intersection of the set of FIDE-rated players and the set of USCF-rated players, which gave a set of players rated in _both_. He then did analysis on these players, which produced _exact_ results for that particular point in time. In no case was a difference of > 100 found at over 2500 rating levels. The USCF formula admits it over-estimates a FIDE rating in deriving it from a USCF rating. Which fits with what Ken found.
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