Leading and Winning
During a basketball game, how big of a point difference could be safe enough to say you have won? Well, it depends on both how much time is left on the clock and how many points a team is ahead.
In this analysis, we investigated 2014-15 NBA regular season games and tried to answer this question. To begin with, 1230 games were played in the past season. 707 of them are won by home teams (57.48%) and 523 of them are won by away teams (42.52%). Thus, home/away is also another significant factor in this debate.
At the end of 3rdQuarter
After three quarters played, here are the facts to foretell the fate of a team at the end of regulation:
When a team led the game after 3rd quarter, they won that game 77.48% of the time. On top of that, when also at home, this probability increased to 79.21%. Below table summarizes the cases according to the home/away factor.
Next, we will look at the most important factor: the effect of the leading points.
To be even more precise, the graph below depicts the winning percentage (orange curve) for all values of points difference after three quarters. If a team leads by 10+ points, they almost surely won that game.
At the end of 2nd Quarter
Let’s now look at the same facts after end of 2nd quarters. It is no-brainer that leading at the half wouldn’t be as advantageous as after the 3rd.
This time, when a team led the game after 2nd quarter, we see that it won that game 67.56% of the time. Approximately %10 less likely than the previous case. Game location (home/away) still applies in favor of home teams.
Let’s pass to the effect of the leading points. Again leading even 0-5 points after 3rd gave almost %10 more chance to win comparing to the leading the same margin at the half.
The following graph shows all the winning percentages for all the leading points after 2nd quarter. Leading 1 or 2 points at half clearly didn’t give any advantage as the winning percentage remained around 50%. In order to increase the chance over 90%, it required to have 16+ points of lead.
At the end of 1st Quarter
Finally, we also analyzed the situation after the first quarter leads.
When a team led the game after 1st quarter, it won that game 62.36% of the time. Around %5 less likely comparing to the 2nd and %15 less likely to win comparing leading after 3rd quarter.
Regarding points difference, 0-10 points lead after 1st gave similar chance to win as it did after 2nd. But if a team had 10+ points of lead after 2nd quarter, it had roughly 10% more chance to win than the same lead after the first. It means that 0-10 points differences before half doesn’t change the fate of a game that much. But if a team opens up a 10+ lead in the 2nd quarter, that begins to be very important for the outcome of the game.
The following graph shows all the winning percentages for all the leading points after 1st quarter. There are more fluctuation in this case as expected.