My family moved to Los Angeles in 1987, just as the Los Angeles Lakers were in the midst of winning back-to-back championships. While I don’t consider myself a huge basketball fan, the NBA finals always hold some interest for me. If you get to watch James Worthy, Michael Cooper, Byron Scott, A.C. Green, Magic Johnson, and Kareem Abdul-Jabbar win championships, it sticks with you.

So now that the Spurs and Heat are competing for the 2013 edition of the NBA championships, I get a little drawn in by the excitement. One of the interesting occurrences from this year’s finals is that the two teams have split the first two games of the series. Listening to ESPN radio, Mike Greenberg mentioned that when the NBA finals are tied 1-1, the winner of game 3 wins the series 92% of the time.

This 92% statistic that’s been such a hot topic this week uses data since the 1985 finals, when the finals switched to being 2 home games, 3 away games, 2 home games for the team with the better record, so I was curious to see whether I can spot a different trend before and after 1985.

I went back to 1967, when the NBA playoffs expanded to 8 teams for the first time. (If you’re into trivia, it was also the first time in 11 years that the Celtics weren’t in the finals.) Since 1967, teams split the first two games in 24 NBA championships.

A graphical analysis of data is always a good way to start. Because the NBA finals have a time component to them, a time series plot lets us check for patterns over time. Plotting the data in time order shows the trend that has been such a strong point of conversation since the Heat won game 2 of the finals. The time series plot below shows a 1 if the team that won game 3 also won the series and a 0 if the team that lost game 3 won the series. The gaps are for years where a team went up 2 games to none.

The time series plot illustrates how strong the advantage has been for the game 3 winners. You can see the comparisons that are in the table below:

 Game 3 winners Game 3 losers NBA Championships 21 3 NBA Championships before 1985 9 2 NBA Championships since 1985 12 1 Longest streak 11 1

Three NBA finals that have been tied 1-1 are particularly easy for me to recall: the 2012 series when the Heat defeated the Thunder in 5 games, the 2001 finals when the Lakers defeated the 76ers in 5 games, and the 1991 finals when the Bulls defeated the Lakers in 5 games. In each of those finals, the team that won the series lost the first game. Because those finals stood out to me, I wondered whether you could find another pattern in series that are tied 1-1: does the eventual winner win the second game more often than the first game?

The following time series plot shows a 1 if the game 1 winner won the series, and a 0 if the game 2 winner won the series.

If that doesn’t look like much to you, you’re right. There are no streaks long enough to seem unusual, but just enough that the oscillation doesn’t seem strange either. In terms of the numbers of finals victories, they’re close in the most obvious ways to look at them. Here’s a table with some comparisons:

 Game 1 winners Game 2 Winners NBA Championships 13 11 NBA Championships before 1985 7 4 NBA championships since 1985 6 7 Longest streak 3 3 Game 3 victors who lost finals 1 2

Even the cases where teams won game 3 and went on to lose the finals (the blue diamonds on the plot) aren’t all on the same side. The plot suggests that it doesn’t matter which of the first two games you win, as long as you get to 2 wins first.

This year, the Spurs won game 3. While a game 4 victory gives the Heat renewed hope, history is still on the side of Tony Parker, Time Duncan, and Manu Ginobili in their quest to win a fourth championship together. It also pushes them closer to the record for playoff wins by three teammates playing together, currently 110 and held by my favorite trio: Magic Johnson, Kareem Abdul-Jabbar, and Michael Cooper.

Finding yourself with a new interest in time series plots? You can check out some quick tips for the time series plot and some other graphs on the Lessons from Minitab Help page!