During this past season, I looked into how adding home ice advantage would change my model for ranking teams. To summarize: there is a home ice advantage in DI women's hockey, but it does little to change the top 8 ranked teams using my model.
I did some more work in preparation for a talk I am giving at the 2009 Joint Statistical Meetings in DC next week, and I wanted to share it and ask for your thoughts.
Using the past 4 seasons of data and looking at just wins, losses, and ties (no game scores), if I assume that HIA (home ice advantage) is the same for every team the estimate of HIA is 0.167. What does this mean in context? If two equal teams are playing, the probability of the home team winning jumps from 41.9% to 48.5%. The probability of a tie is also calculated, so that is why both of these probabilities are less than 50%.
Roughly speaking, if two equal teams played 50 games, a team would win (on average) 21 at a neutral site and 24 if they played at home. Another way to think about it is that playing half of the 34 games in a season at home earns a team 1.1 more wins that if all those games were played at a neutral site.
To investigate things further, I tried to estimate each teams individual home ice advantage. I will skip the details (you can ask if you really want to know), but here are the results for each team, ranked by best home ice advantage, for the last four seasons of games.
Putting these number in context:
When Clarkson plays at home vs. neutral site, the probability of a win increases from 41.9% to 60.2% (assuming equal teams), a gain of 3.1 wins per season (on average).
When Princeton plays at home vs. neutral site, the probability of a win DECREASES from 41.9% to 26.9%. In other words, Princeton losses 2.6 wins a year playing a home vs. neutral ice (on average).
Now, you may argue with the magnitude of these individual home ice advantages, but what I am interested in is the rankings.
Clarkson (very northern New York) and Maine (middle of Maine) have campus locations that can lead to long and difficult travel in winter, while UNH has Olympic sized ice. So these three teams being on top make sense.
It is the lowered ranked teams that I have trouble explaining. Quinnipiac moved to a new rink during this time frame, so we can ignore them for the moment. Robert Morris plays off campus, which explains the lack of home ice advantage.
But what about Princeton and Cornell? Why don't they perform well at home? I have ideas, but I would love to hear your thoughts.
I did some more work in preparation for a talk I am giving at the 2009 Joint Statistical Meetings in DC next week, and I wanted to share it and ask for your thoughts.
Using the past 4 seasons of data and looking at just wins, losses, and ties (no game scores), if I assume that HIA (home ice advantage) is the same for every team the estimate of HIA is 0.167. What does this mean in context? If two equal teams are playing, the probability of the home team winning jumps from 41.9% to 48.5%. The probability of a tie is also calculated, so that is why both of these probabilities are less than 50%.
Roughly speaking, if two equal teams played 50 games, a team would win (on average) 21 at a neutral site and 24 if they played at home. Another way to think about it is that playing half of the 34 games in a season at home earns a team 1.1 more wins that if all those games were played at a neutral site.
To investigate things further, I tried to estimate each teams individual home ice advantage. I will skip the details (you can ask if you really want to know), but here are the results for each team, ranked by best home ice advantage, for the last four seasons of games.
Code:
Maine 0.4635 Clarkson 0.4603 New Hampshire 0.4587 St. Cloud State 0.4352 Syracuse 0.4319 Connecticut 0.3991 Colgate 0.3950 Harvard 0.3615 Wayne State 0.3588 Providence 0.3434 Boston 0.3434 St. Lawrence 0.3214 Minnesota State 0.3071 Rensselaer 0.2809 Wisconsin 0.2743 Bemidji State 0.2679 Mercyhurst 0.1826 Boston College 0.1524 Yale 0.1244 Ohio State 0.1011 Dartmouth 0.0723 Union 0.0715 UMD 0.0581 Brown 0.0567 Niagara 0.0535 Minnesota 0.0531 North Dakota 0.0091 Northeastern -0.0716 Vermont -0.0889 Robert Morris -0.1460 Quinnipiac -0.1834 Cornell -0.3664 Princeton -0.4101
When Clarkson plays at home vs. neutral site, the probability of a win increases from 41.9% to 60.2% (assuming equal teams), a gain of 3.1 wins per season (on average).
When Princeton plays at home vs. neutral site, the probability of a win DECREASES from 41.9% to 26.9%. In other words, Princeton losses 2.6 wins a year playing a home vs. neutral ice (on average).
Now, you may argue with the magnitude of these individual home ice advantages, but what I am interested in is the rankings.
Clarkson (very northern New York) and Maine (middle of Maine) have campus locations that can lead to long and difficult travel in winter, while UNH has Olympic sized ice. So these three teams being on top make sense.
It is the lowered ranked teams that I have trouble explaining. Quinnipiac moved to a new rink during this time frame, so we can ignore them for the moment. Robert Morris plays off campus, which explains the lack of home ice advantage.
But what about Princeton and Cornell? Why don't they perform well at home? I have ideas, but I would love to hear your thoughts.
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