| Sign Up | Google+
 

Beating save percentage to death: Teams

Stay connected for news and updates

 

I used my Even Strength Save Data to look at the effect of Teams. There is not much there.

 

Using the dense data, I constructed the logits (ln(p/(1-p)) myself. I first corrected the observed save percentages for year.

 

> LinearModel.2 <- lm(CalcLogit ~ Team, data=Dataset, weights=ESA)

> anova(LinearModel.2)

 

Analysis of Variance Table

Response: CalcLogit

          Df   Sum Sq Mean Sq  F value Pr(>F)

Team      29   1871.2 64.524   3.8031  1.240e-10 ***

Residuals 895 15184.5 16.966


At a first glance, that looks promising. However, the sum of squares is less than 1/3 the sum of squares we saw for goalies. And we know that teams and individual goalies are highly confounded.


Looking at teams and goalies (with no interaction term)

> LinearModel.4 <- lm(CalcLogit ~ last.first+Team, data=Dataset, weights=ESA)

> anova(LinearModel.4)


Analysis of Variance Table

Response: CalcLogit

           Df  Sum Sq Mean Sq F value Pr(>F)

last.first 231 6041.3 26.153  1.6677  4.121e-07 ***

Team       29   601.9 20.755  1.3236  0.1209

Residuals 664 10412.6 15.682


Adding in goalies, the significance of the team effect goes away.


Looking at teams and goalies (with interaction)


> LinearModel.4 <- lm(CalcLogit ~ last.first*Team, data=Dataset, weights=ESA)

> anova(LinearModel.3)


Analysis of Variance Table

Response: CalcLogit

                 Df Sum Sq Mean Sq F value Pr(>F)

last.first      231 6041.3 26.153  1.6835  9.678e-07 ***

Team             29  601.9 20.755  1.3361  0.1156

last.first:Team 168 2707.5 16.116  1.0375  0.3772

Residuals       496 7705.0 15.534


So the effect of goaltenders remains highly significant. The team effect is not significant, and in magnitude is only about 1/10 that of the goaltenders. Finally, we can compare the models directly, to see if adding in team and the team*goalie interaction adds significance to the model.


> anova (LinearModel.1, LinearModel.3, test="F")

Analysis of Variance Table


Model 1: CalcLogit ~ last.first

Model 2: CalcLogit ~ last.first * Team

  Res.Df RSS Df   Sum of Sq F      Pr(>F)

1 693    11014

2 496    7705 197 3309.5    1.0814 0.249


And it does not.


Conclusion

Using weighted logistic regression, there is not a statistically significant differences between NHL teams in even strength save percentages over the period 1997-2010 if you control for the effect of individual goaltenders.


                                                                                                                                                                                                               

Recent Posts

Stay connected for news and updates

The Next Read

There are 17 Comments. Load Now. Loading

Shortcuts to mastering the comment thread. Use wisely.

C - Next Comment
X - Mark as Read

R - Reply
Z - Mark Read & Next

Shift + C - Previous
Shift + A - Mark All Read

Comment Settings

Live comment alert: Hide it!

Comments for this post are closed.

tracking_pixel_5351_tracker