Friday, April 15, 2011

NBA Playoffs, Game 7: How important is home-court? (First Round)

As the NBA playoffs are upon us, we will hear dozens of clichés thrown around by commentators.  The most irritating cliché is that the home team wins Game 7 of the series most of the time.  Since 1991, the home team is 36-10, a .783 win percentage.  This stat is always brought up without being put into proper context; as if to say having Game 7 at home causes a team to win.  However, I’ve never heard a commentator mention that the team with home-court advantage has a better record and usually is the better team anyway.  One would expect them to win a Game 7 at home, or on the road.  In this article and subsequent articles, I will try to find out how many Game 7s were won by the home team mainly because they were at home. Hit the jump to find out how:

The table below tries to get the answer to the previous question.  The basic premise of the table is that the more road wins there are in a series, the less home-court advantage matters.  I separate Games 1-4 from Games 5-7 because the last three games of a series are probably more intense than the first four and home-court matters slightly, but still materially more in the last three games.  Since 1991, in Games 1-4 the road team wins 32% of the time while in Games 5-7 the road wins 25% of the time.  I rate, on a five point scale, the probability of the home team winning Game 7 mainly because they’re at home.  The five outcomes are: Yes, Probable, Possible, Doubtful, and No.  This is scale far from perfect, but it appears sufficient to answer the question posed in this article. 

Here are two examples of how the table works: The 2004 series between Miami and New Orleans produced no road wins, so it would be safer to say that the home team won Game 7 because of the home court advantage; The 2003 Detroit-Orlando series produced two road wins, Detroit winning that Game 7 was more likely due to them being a better team than due to home-court advantage.  The table below shows the eleven first-round series that went to Game 7 since the first round expanded in 2003. 

The home team won 9 of the 11 Game 7s, but how many of those 9 wins were mainly because of home-court advantage?  According to the table, only 5 of the 9 wins were at least probably due to home-court advantage alone.  That means that 4 of the 9 home-team wins probably had nothing to do with home-court advantage.  Home-court advantage, at least in the first round of the playoffs, seems greatly overstated. Tomorrow, we'll take a look at home-court advantage in the conference semifinals.

There's A Stat For That

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