## Simulating GGVT

In a previous post, I looked at simulating GVA.  Here I simulate goaltender performance and calculate the goaltender portion of GVT.

In a previous post, I looked at simulating goaltender performance and calculating GVA. I found that observed values of GVA could be obtained from an average goaltender and random factors. I also found that GVA is fairly imprecise with a relatively large standard deviation and wide confidence interval. I would think GVT would perform similarly to GVA. To explore this, I ran some simulations using a pseudo-random number generator. For these simulations I used ES threshold save percentage of 0.914, PK threshold save percentage of 0.863, and PP threshold save percentage of 0.911. I used the results to calculate the goaltender portion of GVT (GGVT). For these simulations, I did not attempt to calculate puck handling or shoot out contributions. As I found in my last post, the GGVT value I calculated is not quite what Gabe's tables show. As such, I call my statistic GGVT*.

The average NHL team in 2009 faced 2478 shots, 1971 at even strength, 437 on the penalty kill, and 70 on the power play. If a hypothetical starter played 2/3 of his teams minutes, he faced 1314 shots at ES, 291 on the PK, and 47 on the PP. The average goaltender had ES save percentage of 0.917, PK 0.868 and PP 0.914. Running 10,000 simulated seasons gives:

GGVT*

Min. :-34.459

1st Qu.: -1.460

Median : 4.540

Mean : 4.157

3rd Qu.: 9.790

Max. : 39.791

Std. Dev. 8.798131

Thus a 95% CI for GGVT at this workload is [21.401, -13.087]

I ran simulations for each actual goaltender workload. The data for this is in the appendix below. Ryan Miller and Tuukka Rask had GVT values that are above the 95% confidence interval and Vesa Toskala and John Curry had GVT values that are below the 95% confidence interval.

Conclusion

The range of GGVT* seen in a single season can be duplicated by an average goaltender and random factors. Extreme values of GGVT* do lie outside the 95% CI for average GGVT*.

As an estimate of goaltender performance, GGVT* is subject to estimation error. This simulation data suggests that observed GGVT*, like GVA, is a fairly imprecise estimate, with a large standard deviation and a large confidence interval.

Acknowledgments

Again, I want to thank Sunny Mehta for his very helpful correspondence. I also want to thank Tom Awad for his patient and thoughtful discussions of GVT.

Appendix

GVTact : actual GGVT from the 2009-2010 season

Max : maximum GGVT* seen in the simulation at this workload

Min : minimum GGVT* seen in the simulation at this workload

Mean : average GGVT* seen in the simulation at this workload

StdDev : standard deviation of GGVT* seen in the simulation at this workload

Upper CI : upper limit of the 95% confidence interval

Lower CI : lower limit of the 95% confidence interval

 Name GGVTact Max Min Mean StdDev Upper CI Lower CI MillerRyan 38.5 52.06 -37.94 7.06 13.1 32.74 -18.63 VokounTomas 31.5 53.05 -49.95 6.79 13.14 32.54 -18.95 NabokovEvgeni 30.5 56.71 -52.29 7.37 13.64 34.1 -19.35 HowardJimmy 26.8 49.26 -37.74 5.86 12.27 29.92 -18.19 RaskTuukka 24.9 42.97 -32.03 4.21 10.02 23.86 -15.44 BryzgalovIlya 26 56.08 -49.92 6.86 12.81 31.97 -18.25 KiprusoffMiikka 25.7 53.96 -40.04 6.96 12.97 32.38 -18.46 LundqvistHenrik 28.3 56.54 -44.46 6.76 13.05 32.34 -18.82 HalakJaroslav 21.7 43.68 -43.32 4.58 10.7 25.56 -16.4 AndersonCraig 21.9 60.86 -44.14 7.42 13.73 34.33 -19.49 HillerJonas 20.9 52.71 -42.29 6.26 12.33 30.42 -17.9 BrodeurMartin 17.1 55.06 -38.94 6.63 12.92 31.96 -18.7 WardCam 13.1 46.27 -39.73 4.8 10.85 26.05 -16.46 ConklinTy 10.9 30.87 -33.13 2.59 8.03 18.34 -13.16 HedbergJohan 12.3 44.94 -40.06 4.73 10.53 25.37 -15.91 LaBarberaJason 8.7 22.21 -23.79 1.57 6.3 13.92 -10.79 MasonChris 13.8 51.37 -47.63 5.77 11.92 29.14 -17.6 LuongoRoberto 14.5 55.47 -55.54 6.47 12.58 31.12 -18.18 TurcoMarty 10.6 61.34 -38.66 5.41 11.51 27.96 -17.14 ThomasTim 9.6 39.16 -33.84 4.21 9.94 23.69 -15.28 BrodeurMike 4.1 8.5 -10.5 0.33 2.7 5.62 -4.95 PriceCarey 8.4 41.16 -43.84 4.21 10.31 24.42 -16.01 BernierJonathan 3.8 8.86 -10.14 0.3 2.77 5.72 -5.13 NiemiAntti 6 34.18 -30.82 3.12 8.88 20.52 -14.29 TheodoreJose 7.4 40.55 -40.45 4.52 10.8 25.68 -16.64 KhudobinAnton 2.7 4.75 -8.25 0.2 2.02 4.16 -3.77 NiittymakiAntero 6.1 45.11 -38.89 4.89 10.8 26.06 -16.28 BudajPeter 3.9 22.03 -23.98 1.31 5.63 12.35 -9.72 DanisYann 2.8 14.25 -16.75 0.74 4.12 8.81 -7.34 RinnePekka 7.7 47.41 -35.59 5.1 11.23 27.12 -16.92 ElliottBrian 6.6 46.96 -40.04 4.85 10.86 26.14 -16.44 NeuvirthMichal 3.6 21.63 -23.37 1.62 6.11 13.6 -10.36 ClemmensenScott 3.7 26.64 -28.36 2.15 7.41 16.68 -12.38 GreissThomas 2.8 21.66 -24.34 1.29 5.74 12.55 -9.96 LehtonenKari 1.9 19.44 -21.56 1.26 5.38 11.81 -9.29 JohnsonChad 1.6 11.65 -14.35 0.42 3.32 6.93 -6.1 RaycroftAndrew 2.9 23.64 -23.36 1.41 5.92 13.01 -10.19 SchneiderCory 0.5 5.44 -8.56 0.18 2.2 4.49 -4.12 PechurskiAlexander 0.2 1.27 -5.73 0.04 1.05 2.1 -2.02 CrawfordCorey 0.2 3.27 -6.73 0.11 1.69 3.43 -3.2 BacklundJohan 0.2 2.22 -6.78 0.07 1.39 2.79 -2.66 LalimePatrick 1.1 22.6 -21.41 1.53 5.98 13.25 -10.2 KhabibulinNikolai 2.2 27.11 -23.89 1.93 7.09 15.83 -11.98 VarlamovSemyon 3.7 31.46 -27.54 2.57 7.7 17.66 -12.51 EllisDan 2.9 34.81 -29.19 2.86 8.35 19.23 -13.5 ErsbergErik 0.6 16.8 -19.2 0.79 4.48 9.57 -7.99 GiguereJean-Sebastien 2.8 36.14 -30.86 3.49 9.24 21.6 -14.62 ZabaMatt -0.3 1.69 -6.32 0.05 1.22 2.43 -2.34 DuchesneJeremy -0.4 0.4 -2.61 0.01 0.59 1.16 -1.14 EnrothJhonas -0.4 3.46 -7.55 0.09 1.77 3.56 -3.37 PetersJustin 0.3 16.59 -15.41 0.83 4.41 9.46 -7.8 LegaceManny 2.5 29.12 -28.88 2.49 7.83 17.84 -12.86 JohnsonBrent 1.3 26.32 -26.68 1.77 6.63 14.78 -11.23 TokarskiDustin -1.1 1.43 -4.57 0.05 1.11 2.23 -2.13 DubielewiczWade -1.2 3.39 -6.61 0.13 1.72 3.51 -3.24 ClimieMatt -1 3.38 -8.62 0.11 1.71 3.46 -3.25 EmeryRay 2.1 34.81 -28.19 2.63 8.1 18.52 -13.25 McElhinneyCurtis -0.2 24.82 -23.18 1.71 6.61 14.67 -11.26 SalakAlexander -1.6 4.12 -7.88 0.12 1.87 3.8 -3.55 PavelecOndrej 2.5 40.47 -36.54 4.65 10.65 25.52 -16.22 DipietroRick -0.3 13.27 -15.73 0.62 4.01 8.47 -7.23 MacDonaldJoey -1.4 12.1 -16.9 0.51 3.64 7.65 -6.64 LeightonMichael 2 35.54 -33.46 3.08 8.67 20.07 -13.91 QuickJonathan 5.5 60.58 -41.42 6.47 12.81 31.57 -18.64 CurryJohn -2.7 1.12 -4.88 0.05 0.99 2 -1.9 HardingJosh 0.5 28.25 -30.75 2.17 7.56 16.98 -12.65 RolosonDwayne 3.4 41.99 -39.01 5.17 11.37 27.46 -17.12 GaronMathieu 0.6 33.28 -33.72 2.94 8.45 19.5 -13.62 FleuryMarc-Andre 3.9 49.88 -41.12 6.14 12.22 30.09 -17.81 ValiquetteSteve -4.8 11.39 -13.61 0.42 3.28 6.85 -6.01 GustavssonJonas -1.2 38.59 -32.41 3.81 9.81 23.04 -15.43 BoucherBrian -1.4 31.08 -30.92 2.63 8.09 18.49 -13.23 BironMartin -4.7 35.13 -25.87 2.98 8.41 19.47 -13.51 AuldAlex -3.8 23.01 -24.99 2.02 7.11 15.95 -11.91 BackstromNiklas 0.4 52.66 -39.34 5.54 11.65 28.38 -17.3 DubnykDevan -6.2 28.58 -27.42 1.94 6.87 15.41 -11.53 SmithMike -2.6 45.24 -36.76 4 9.76 23.14 -15.13 MasonSteve -1.5 46.69 -39.31 5.57 11.91 28.91 -17.76 DeslauriersJeff -3.6 44.91 -39.09 5.3 11.21 27.27 -16.67 OsgoodChris -6.8 25.52 -24.48 1.87 6.83 15.26 -11.52 HuetCristobal -7 42.03 -32.97 3.65 9.4 22.07 -14.77 LeclairePascal -9.7 32.98 -28.02 2.92 8.37 19.32 -13.48 ToskalaVesa -13.8 33.25 -34.75 2.66 8.08 18.49 -13.17

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