ranking is based on his performance in the elite tour- naments that are held six times a year. Each wrestler has fifteen bouts per tournament, one per day over fifteen consecutive days. If he fin- ishes the tournament with a winning record (eight victories or better), his ranking will rise. If he has a losing record, his ranking falls. If it falls far enough, he is booted from the elite rank entirely. The eighth victory in any tournament is therefore critical, the difference between promotion and demotion; it is roughly four times as valuable in the rankings as the typical victory. So a wrestler entering the final day of a tournament on the bubble, with a 7-7 record, has far more to gain from a victory than an oppo- nent with a record of 8-6 has to lose.     Is it possible, then, that an 8-6 wrestler might allow a 7-7 wrestler to beat him? A sumo bout is a concentrated flurry of force and speed and leverage, often lasting only a few seconds. It wouldnt be very hard to let yourself be tossed. Lets imagine for a moment that sumo wrestling is rigged. How might we measure the data to prove it? The first step would be to isolate the bouts in question: those fought on a tournaments final day between a wrestler on the bubble and a wrestler who has already secured his eighth win. (Because more than half of all wrestlers end a tournament with either seven, eight, or nine victories, hundreds of bouts fit these criteria.) A final-day match between two 7-7 wrestlers isnt likely to be fixed, since both fighters badly need the victory. A wrestler with ten or more victories probably wouldnt throw a match either, since he has his own strong incentive to win: the $100,000 prize for overall tournament champion and a se- ries of $20,000 prizes for the "outstanding technique" award, "fight- ing spirit" award, and others. Lets now consider the following statistic, which represents the hundreds of matches in which a 7-7 wrestler faced an 8-6 wrestler on a tournaments final day. The left column tallies the probability, based