Home-Court ‘Edge’ Confounds Experts

On Feb. 29, you ran a statistical blurb saying that “home-court advantage in the playoffs . . . is a considerable edge” and showing the annual percentages of NBA playoff series won by the home team. In total, since 1990-91, 74.8% of playoff series have been won by the team with home-court advantage.

This is not evidence of home-court advantage. The team with home-court advantage is often simply the better team, as indicated by their superior regular-season record. The fact that these teams win 74.8% of their series may be attributed to their superior talent rather than home-court advantage.

This is a classic case of what we statisticians call a “confounding factor,” and I plan to use this example in my elementary statistics classes at UCLA. A better way to examine the significance of playoff home-court advantage is to compare the percentage of games won by the home team, since both the stronger and weaker teams get to play games on their home court. A slight problem is that the better teams get to play more games on their home court, but this problem is rather negligible. In the last 10 finals series for instance, the home team has won only 29 of the 56 games, or 51.8%. Apparently, home-court advantage in the NBA finals is not significant.

The best-kept secret in basketball is that there is no such thing as home-court advantage in the playoffs. The reason teams have worse records on the road during the regular season may be due to the weariness caused by travel. During the playoffs, however, both teams travel equally.

RICK PAIK SCHOENBERG

Professor of Statistics, UCLA