Patrick D. (SnarkSD)
January 10 2013 04:15PM

This stastistical study of the percentages (aka: PDO) came to us from Shark Fan and writer SnarkSD. It is an in-depth, thorough investigation, so be sure to settle in for a long, but interesting, read. We will try to answer any questions in the comments for anyone not well versed in statistical theory.


Objective: Define the standard deviation in all strength non-shootout, and even-strength excluding empty net PDO (the sum of shooting percentage and save percentage). Separating the variance into that accounted for by chance, and that accounted for by talent. Investigate variables that may influence PDO. Calculate Points-Per-Game (aka, Expected Points, or EP) for a league average team, given a non-one PDO.

Methods: Data from the 2005-2006 through 2011-2012 season was extracted from game-logs and imported into excel and STATA to generate linear and logistic models for all strength data. Data was imported from for even strength excluding empty net data. A program in excel was created to randomly select games, generating thousands of iterations for each regression model, with the average of these models shown below. To generate chance data, the normal approximation interval for binomial proportion confidence intervals was used.

Results: The standard deviations, correlations, and standard error of the model over different samples of games was generated and depicted in table 2. Eg. 1 SD at 30 games for all teams (N=210) is 0.0174, with 1 SD for chance being 0.0140. Figure 2 demonstrates Table 2 over a set of 82 games. Teams that fall outside the red line represent ±3 SD from chance, and are therefore highly likely to be suffering from a low or high PDO from poor or exceptional performance, respectively. League average points-per-game (EP) for a single game is shown in Figure 3. Figure 4 demonstrates EP for multiple game samples.

Conclusion: PDO has boundaries of normal variance, both in observed variance, and variance strictly by chance. With the data below one can measure the expected performance in points-per-game for a given PDO. A deviation from the expected results (ie. points-per-game) indicates a deviation in performance outside of PDO, likely the result of shootout and OT performance if not corrected for, followed by factors that influence PDO intra-game, shot%, home/road, and competition.

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Why an Ilya Bryzgalov/Rick DiPietro trade would be the best thing ever

Jonathan Willis
January 10 2013 12:59PM

Photo: Michael Miller/Wikimedia

If the Philadelphia Flyers really are – as Wednesday’s edition of the Roberto Luongo rumour mill suggests – interested in buying out Ilya Bryzgalov, they should stop and not do that. I’m not saying they need to keep Ilya Bryzgalov – just that if it is within their power they should trade him to the New York Islanders and buyout Rick DiPietro instead.

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Number Chains - January 8th Links

Josh L.
January 08 2013 04:50PM



This new, regular feature on NHLNumbers will share interesting stats-related posts from around the web almost every day.

Welcome. In this space you will be able to find the best analytical hockey writing from around the internet on a close-to-daily basis. Subject matter will include statistical evaluation, financial analysis, contractual issues, and (sometimes) closely-related tangential works. If you have something you would like to submit for a future edition (your writing or that of someone else) feel free to send it to me via Twitter @JoshL1220 or leave a comment.

David Rogers of Awful Announcing starts us off today with a story about the laughable coverage the NHL Network has provided of the lockout.

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Remaining RFAs of Interest

Kent Wilson
January 08 2013 01:39PM

The lock-out interrupted a lot of things this year, not the least of which was free agency. Most of the big (and middle sized) fish were signed to some famously controversial deals last summer, but more than a few significant loose ends were left when the prior CBA expired in September.

The most significant of which is a collection of young, burgeoning restricted free agents, several of whom figure to be major cogs for their current clubs for years down the road. As of right now, however, a bunch of these guys remain without a deal and are therefore open to an offer sheet or two (new CBA permitting, of course).

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Alexei Kovalev returns to the NHL, maybe

Jonathan Willis
January 08 2013 10:21AM

Photo: Michael Miller/Wikimedia

On Tuesday morning, the Miami Herald’s George Richards reported that Alexei Kovalev, the veteran of more than 1,300 NHL games and a guy with more than 1,000 points, will be in training camp with the Florida Panthers.

What should be expected of him?

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