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05-04-2013, 05:51 PM
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Megalodan
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Stupid Spreadsheet Tricks - Expected Wins

Basic facts:
  • Hockey teams win games by outscoring their opponent; therefore, a simple indicator of a team's seasonal success is the number of goals scored against goals allowed.
  • The NHL's 'goal differential' (goals scored - goals allowed) is misleading because it does not account for the quantities of each, only the difference between them.
  • A better indicator is "Goals per Goals Against". This ratio indicates the ability of a team to outscore their opponent on any given night, by comparing goals scored directly to goals allowed.

There are several variations and interesting experiments that can be done with this stat, but my favorite is calculating how many games a team can expect to win with their 'goal ratio'.

If we assume that a team with a 1.00 ratio (exactly one goal scored for every goal allowed) will win exactly half of their games, then we can calculate the number of games a team should have won:
Code:
Expected Wins  = [ ( Goals For per game) / (Goals Against per game) ] * (# of games in season / 2)

note: whether you use "goals" or "goals per game" does not matter since they are (almost) the same and the denominators will cancel out
If you run that against the 2013 stats (as well as other seasons) you will get a table like the one below. The teams are ranked by the number of wins they had this season. The expected wins for each team is also calculated, and a second ranking is made based on this stat. A 'differential' indicates how many ranks a club 'unfairly' rose or fell from expectations. The numbers are hauntingly accurate.

Please leave any questions, comments, or criticisms for me. I've done this as a hobby for the last few seasons, and this is the first time I've wrote up anything about. Thanks for reading.

Rank Team GP WL OT G/G GA/G Goals/GAExpected WinsExp. RankRank. Diff
1CHICAGO4836753.12.021.53465346536.8310
2PITTSBURGH48361203.382.481.36290322632.7120
3ANAHEIM48301262.792.41.162527.9063
4MONTREAL48291453.042.581.17829457428.2840
5ST LOUIS48291722.582.381.08403361326.02127
6BOSTON48281462.652.211.19909502328.783-3
7LOS ANGELES48271652.732.381.14705882427.5370
8WASHINGTON48271833.042.711.12177121826.9291
9VANCOUVER48261572.542.41.05833333325.40134
10TORONTO48261753.022.671.13108614227.158-2
11NY RANGERS48261842.622.251.16444444427.955-6
12MINNESOTA48261932.462.60.94615384622.71208
13SAN JOSE48251672.422.331.03862660924.93141
14OTTAWA48251762.332.081.12019230826.8810-4
15DETROIT48241682.542.291.10917030626.6211-4
16COLUMBUS48241772.42.4124.0015-1
17NY ISLANDERS48241772.812.830.99293286223.83170
18WINNIPEG48242132.622.940.89115646321.39246
19PHILADELPHIA48232232.752.90.94827586222.76190
20DALLAS48222242.672.940.90816326521.80222
21PHOENIX48211892.522.60.96923076923.2618-3
22BUFFALO48212162.462.90.84827586220.36253
23NEW JERSEY481919102.292.540.90157480321.64230
24EDMONTON48192272.562.730.93772893822.5121-3
25CAROLINA48192542.653.310.8006042319.21283
26CALGARY48192542.673.270.81651376119.60271
27TAMPA BAY48182643.063.06124.0016-11
28NASHVILLE48162392.272.770.81949458519.6726-2
29COLORADO48162572.383.120.76282051318.31290
30FLORIDA48152762.273.540.64124293815.39300

The clubs that are closer to a 1.00 goal ratio are more likely to rise/fall in the standings unfairly. I hypothesize that this fluctuation is based on the number of overtime games these clubs play, and their ability to take wins out of them.

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