I watched CMS play Pomona-Pitzer in the 5C rivalry game last night. CMS had 20 defensive rebounds (28 overall) and Pomona-Pitzer had 26 defensive rebounds (31 overall), so at first glance you would say that Pomona had a better rebounding game. But a look at the data reveals CMS was the far better rebounding team during the game. Why?
CMS missed 34 shots and Pomona rebounded 26, which gives them a 76.5% rebound share. At the other end Pomona missed 25 shots and CMS rebounded 20, which gives them a 80% rebound share. Inversely, CMS rebounded 23.5% of its own misses and Pomona rebounded only 20%. The key thing to note is that CMS had more chances than Pomona, so naturally Pomona would rebound more of CMS's missed shots.
Box scores don't do a very good job of presenting rebound statistics. I've seen many coaches make the above mistake. They present the data so that the obvious comparison is between one team's defensive rebounds and the other team's defensive rebounds. The problem with doing it this way is these teams are rebounding at different baskets. Some games, one team will have way more shots than the other team due to turnovers or free throws or whatever. This means that the defense will have far more opportunities to get rebounds than the offense, because there are going to be more missed shots. The better way to look at the data is to compare one team's defensive rebounds with the other team's offensive rebounds, and compare the proportions.
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