Author: James T. Walker
Date: 05:30:19 08/27/00
Go up one level in this thread
On August 26, 2000 at 14:46:08, Stephen A. Boak wrote: >In below threads, there is discussion about comparing performances of various >programs using 1) Ranking or average Ranking (for 'teams') or 2) TPR - >Tournament Performance Rating or average TPR (for 'teams'). > >I suggest that using 2) TPR as a measure of which program (or team) is best is >inappropriate under many circumstances, including the circumstances of the just >concluded WMCC competition where the ratings of the participants varied >greatly. > >Examples: > >My rating is approx 1900. Let's say I play in a 4-round tournament in an >appropriate class section (Under 2000 rating--which typically includes mostly >1800 to 1999 rated players) that happens to several very weak entrants--possibly >up and coming young players that wish to get tougher competition to foster their >chess development. > >Example 1: > >Assume I play the following opponents, and have the following results: > Ro Pts GPR (Game Perf Rtg--using +/- 400 rule for TPR calc) >1300 1 1700 >1950 0 2350 >1975 1 1575 >1960 0.5 1960 > TPR 1896 > >In this example, my TPR (1896) is less than my current (starting) rating of >1900, despite the fact that I scored 1.5 / 3 against better players and 1 / 1 >against lower rated players--all results better than my expected average scores >against such rated opponents. > >Clearly I performed better than a typical 1900 player would (on the average), >yet my TPR is lower than 1900 (my current start rating). Why? > >The best TPR you can achieve is limited when you play players far below your >rating. Even if you beat one of them (above, in the example, I beat a 1300 >player, 600 points lower than my rating), that result will 'artificially' lower >your average TPR for the tournament. > >Example 2: > >In a small local tournament, my rating (1900) is by far the highest among all >the remaining, low rated, participants. I play four 1300 players and beat them >all, in a 4-round event, my TPR will be 1700 (limited by their low ratings). > >ELO Systems are better. > >By USCF rating rules (ELO-based), I will gain a few rating points (approx. 9 >points increase) for my performance in the Example 1 tournament. I might gain 1 >to 4 points (maximum) in Example 2. > >CONCLUSION: > >TPRs are most useful and meaningful for comparative purposes when: > >1. A compared program has a well-established rating (not perfect, but based on >many prior games and results against rated opponents). > >2. Large numbers of games are included in the TPR calculations (say 20 or more). > >3. The games included in the TPR calculations are against a wide variety of >opponents, rated both above and below your mean (average) rating. > >With many games, against a wide variety of opponents, both above and below your >rating, the possible TPR skewing due to playing an occasional player well above >or below your rating is relatively small when averaged in the TPR calculation >for many games. > >ELO formulas, however, take into account both your and your opponent's ratings, >in order to determine statistical expectancies for scoring. When you perform >better than expected based on starting ratings (score more points than expected) >your rating will increase. The opposite will occur when you perform worse than >expected. > >By contrast, TPR used for comparison purposes has its limitations. For a single >Swiss pairing tournament, the pairings of the individual programs may greatly >differ, depending on which programs score better early in the tournament and >which score better late in the tournament. Two programs that tie in final score >may have significantly different TPRs--not due to the inherent abilities of the >two programs, but due to the random factors involved in the pairings during the >entire tournament. > >The large number of relatively weaker participants in the recent WMCC >competition lead to TPRs that are not very useful for comparing performances. > >--Steve Hello Steve, It seems to me you are trying to compare apples to oranges. TPR is used for unrated players to only approximate their performance in a single tournament. If you play enough games in the single tournament you may receive a "Provisional" rating based on your performance. Once you have an established rating (20 games in USCF) the TPR has no real significance except it may give you a quick idea of how well you have done compared to how well you should have done. Even with an established rating it is only an approximation within a range. Jim Walker
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