Blackhawks' streak strains the laws of probability

Blackhawks' streak strains the laws of probability

March 7, 2013, 7:00 pm
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As good as the Blackhawks have been, it takes a bit of good fortune to play 24 games in the NHL, and accumulate a point in every single one. But how much good fortune?

Stephen Stigler, PhD, professor of statistics at the University of Chicago since 1979, says it's a matter of determining how good the Blackhawks really are, but their run is not as improbable as it sounds.

"They are not violating the laws of nature in the probability of what's been happening," said Dr. Stigler.

As Stigler explained, with all things being equal, the chance of an average team getting a point in a single game is .75 (or 75 percent). Under those circumstances, "the chance of getting a point in 24 straight games, well then it's one-in-1000."

Obviously, the Blackhawks are not an average team and Stigler acknowledged that this model was too simple for figuring out how unlikely their run has been.

To dig deeper, Stigler started by determining the probability of a team winning 18 out of 24 games in regulation. For an average team, Stigler calculated that the chances of winning 18 out of 24 to be one-in-100. Stigler then adjusted the formula to "correspond to data on top teams" and changed the probability in his formula that the Blackhawks would win any game to 60 percent. With that assumed, Stigler calculated the probability of the Blackhawks winning 18 out of 24 as one-in-10.

"Not that extraordinary," Stigler said. "What makes it a bit more extraordinary is if you factor in also the chance that of the non-wins, they were all ties."

Since the Blackhawks have gone 3-3 in shootouts, Stigler classified them ties for the sake of his calculation, and pitted the probability of the Blackhawks not having a single overtime loss at two-in-50. The odds of 18 regulation wins and no overtime losses happening at the same time?

"What we're observing has a chance of about one-in-50," Stigler said.

For the Blackhawks to repeat the feat in the second half of the season, there are more factors at work than simply nailing another one-in-50 shot. Stigler himself acknowledged "The Blackhawks have been incredibly healthy."

Ryan Wagman of Hockey Prospectus identified the Blackhawks' defense as a driving -- and possibly luck-related -- factor in the Blackhawks' success. He pointed out that the Blackhawks' team save percentage (.933 through Thursday) was well-above what the career averages of Corey Crawford and Ray Emery would suggest is sustainable.

However, Wagman also identified the Blackhawks' shooting percentage (the rate of shots on goal that resulted in scores) as being at a unexpectedly low 8.99 percent on Feb. 26th, and predicted that it would rise to a degree that would cancel out the harm done by a decline in goaltending performance.

"The pieces are in place for an historic regular season," Wagman said, "Outside of injuries (debatably) their current record is not the result of rampant good luck but of a well-built team."

No team goes 24 games without a regulation loss without beating the odds, but a well-built roster can go a long way toward making the game looked fixed. Even though the math says otherwise, Stigler understands if people start to think that chance is no longer part of the equation.

"The inference to be made is that the Blackhawks are playing at a level that they're almost certain to win every night," he said.