BZS 2.0: Ironing Things Out a Bit

Some of you remember my post from awhile ago where I put together the Balanced Zone Shift (BZS) statistic by establishing the Expected Zone Shift from a 4-year NHL sample.  You'll also recall by the date on the post that I used 2010-11 data essentially from midseason, and didn't use regression to iron out the Expected Zone Shift.  So I wanted to take care of both of those things in this post.

If you'll remember, Expected Zone Shifts gave me a graph that looked like this (Zone Start% ranges on the X-axis, Expected Zone Shifts on the Y):

Nhl_expected_zone_shift_2007-08_to_2010-11_medium

Well, that left me with those lovely little ripples that I eventually planned on getting off my ass to smooth out.  So I did a couple of things:  included full 2010-11 season data, altered my player sample to include all playing seasons where the player played at least 30 games (I had used 50 games previously), used additional sample adjustments including only using 5v5 data and 5v5 TOI of a minimum 10min/60 for forwards and 12min/60 for defensemen, and doing the aforementioned regression between O-Zone Start% and Zone Shift.  The resulting model from a sample of 2,063 playing seasons over the years 2007-08 through 2010-11 for Expected Zone Shift:

Expected Zone Shift = (O-Zone Start% multiplied by -0.701807038) + 35.17679547

You'll want to make sure that O-Zone Start% is expressed XX.X..., not as 0.XXX...

To get BZS, I just subtract the Expected Zone Shift from the actual Zone Shift for the player.

For those who want a handy guide for eyeballing a player's value via Zone Starts and Finishes:

O-Zone Start% Expected Zone Finish% Expected Zone Shift
< 35 --- 12.50
35.00 45.61 10.61
36.00 45.91 9.91
37.00 46.21 9.21
38.00 46.51 8.51
39.00 46.81 7.81
40.00 47.10 7.10
40.50 47.25 6.75
41.00 47.40 6.40
41.50 47.55 6.05
42.00 47.70 5.70
42.50 47.85 5.35
43.00 48.00 5.00
43.50 48.15 4.65
44.00 48.30 4.30
44.50 48.45 3.95
45.00 48.60 3.60
45.25 48.67 3.42
45.50 48.74 3.24
45.75 48.82 3.07
46.00 48.89 2.89
46.25 48.97 2.72
46.50 49.04 2.54
46.75 49.12 2.37
47.00 49.19 2.19
47.25 49.27 2.02
47.50 49.34 1.84
47.75 49.42 1.67
48.00 49.49 1.49
48.25 49.56 1.31
48.50 49.64 1.14
48.75 49.71 0.96
49.00 49.79 0.79
49.25 49.86 0.61
49.50 49.94 0.44
49.75 50.01 0.26
50.00 50.09 0.09
50.25 50.16 -0.09
50.50 50.24 -0.26
50.75 50.31 -0.44
51.00 50.38 -0.62
51.25 50.46 -0.79
51.50 50.53 -0.97
51.75 50.61 -1.14
52.00 50.68 -1.32
52.25 50.76 -1.49
52.50 50.83 -1.67
52.75 50.91 -1.84
53.00 50.98 -2.02
53.25 51.06 -2.19
53.50 51.13 -2.37
53.75 51.20 -2.55
54.00 51.28 -2.72
54.25 51.35 -2.90
54.50 51.43 -3.07
54.75 51.50 -3.25
55.00 51.58 -3.42
55.50 51.73 -3.77
56.00 51.88 -4.12
56.50 52.02 -4.48
57.00 52.17 -4.83
57.50 52.32 -5.18
58.00 52.47 -5.53
58.50 52.62 -5.88
59.00 52.77 -6.23
59.50 52.92 -6.58
60.00 53.07 -6.93
61.00 53.37 -7.63
62.00 53.66 -8.34
63.00 53.96 -9.04
64.00 54.26 -9.74
65.00 54.56 -10.44
> 65 --- -12.50
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