Boston versus the field

Since the NBA playoffs are starting today, I figured I’d throw out my own predictions. I used something I call “True Winning Percentage” (which I will explain some other time, but essentially, it takes into account opponent’s records, and opponents’ opponents’ records, and opponents’ opponents’ opponents’ records, and so on, and determines what a team’s “true” winning percentage would be if they played each other team infinite times, at least, theoretically), to calculate odds for each first round matchup, and then compared those projected winners and so on. Here are my predictions, along with my estimated probabilities of each team I pick to win actually winning the series:

Likely victor Probability of likely victor winning series
BOS>ATL 0.8509
CLE>WAS 0.5313
ORL>TOR 0.6414
DET>PHI 0.7266
LAL>DEN 0.6114
HOU>UTA 0.543
SAN>PHO 0.5303
NOR>DAL 0.5753
BOS>CLE 0.7829
DET>ORL 0.5894
LAL>HOU 0.5257
SAN>NOR 0.513
BOS>DET 0.6384
SAN>LAL 0.5004
BOS>SAN 0.6198

Note that the matchup between San Antonio and LA is essentially a dead heat. However, Boston has essentially identical odds against both, so the final outcome is not so much in doubt.

I also calculated overall odds of each playoff team winning the title, given their probability of winning against each other playoff team, these odds are as follows:

Team True Win% Prob of championship
bos 0.8106 0.7753
sa 0.7242 0.0496
lal 0.7239 0.0491
no 0.7137 0.0352
det 0.708 0.0292
hou 0.7029 0.0247
pho 0.6993 0.0219
uta 0.6657 0.0071
dal 0.6479 0.0039
orl 0.6281 0.002
den 0.625 0.0018
cle 0.5427 9E-05
was 0.5115 3E-05
tor 0.4857 9E-06
phi 0.477 6E-06
atl 0.4285 8E-07

As you can see, Boston has better than 3:1 odds of winning before any basketball has even been played. They are just that much better (even taking into account that they played most of their games against weaker competition) than everyone else. Incidentally, to see the effect of calculating True Win%, notice that Detroit, which had the second best win-loss record, falls to fifth when you take into account their opponents’ (and so on…) success. To conclude, given that the odds of any other team winning come in at 22.47%, I feel pretty safe picking the Celtics this year.

Notice that I don’t predict much success for Utah, contrary to several other prognostications that have them performing very well in the playoffs. I understand that these other folks are using scoring efficiencies and the like, but I’m sticking to my guns. Consider this my bold prediction: Houston will actually beat Utah in the first round (although it will be close).

2 responses to “Boston versus the field

  1. David,

    Can you give a little more insight into how you calculated each team’s probability of winning the championship?

    The probability of a team winning the championship should be equal to the product of the probabilities of the given team winning each round given the team makes it to that round. Taking your round-by-round win probabilities for the Celtics versus the most likely opponents and adjusting them upward a bit to account for the potential of facing weaker opponents (except for the first round, since the opponent is known) , I get roughly a 35% chance of them winning the championship, which intuitively seems much more reasonable than 78%.

    Looking at it another way, the fact that you’re giving Boston a 77.5% chance of winning the title and a 85.1% chance of winning round 1, this implies that the Celtics have a ridiculous 91.1% chance of advancing through the next three rounds given they make it past Atlanta.

    I’ve been a fan of your recent analyses (and graphics), but this just doesn’t seem to add up. Is there something that I’m missing?

  2. rapidadverbssuck

    I did the original odds analysis in a very lazy way. I just found the chance of each team beating each of the other teams, and normalized those odds to sum to zero. Since this isn’t actually how the playoffs are played (obviously), it’s pretty poor analysis. However, your comment encouraged me to actually do a more thorough analysis, which I’ve posted. In this second analysis, I predict the most likely winner of each round, and then each team’s probability of beating an Expected Value version of their second round opponent, and so on to the title. Thanks for your interest and your pushing me a little on the analysis. I need to be kept honest.

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