Playing with Score Effects

[Doctor No]

An underlying hypothesis of score effects is that when a team is trailing, they take more shots on net in a deliberate trade between (increasing) quantity and (decreasing) quality.

A consequence is that winning goaltenders will (a) face more shots on average, and (b) have a higher save percentage.

This is a thread where I'll put interesting (to me) tables as I develop adjustments for my goalie data models.

Click to read more...

 

[Doctor No]

2017-18 NHL regular season, since it's complete. Shots and saves by period (just to get a baseline).

We all understand that save percentages are lower in overtime (significantly). They are also lower (with more shots faced) in the second period, where the change is longer for both teams.

	SV	SH
1st	24,283	26,440	0.918
2nd	25,102	27,678	0.907
3rd	23,287	25,459	0.915
OT	1,094	1,287	0.850

[TBODY] [/TBODY]

 

[Doctor No]

2017-18 NHL regular season data, split by the score at first intermission. "I1D" reflects the goaltender's team position at the first intermission - for instance, "2" means that the goaltender's team is ahead by two at the intermission. Shots and saves in the table below reflect second-period data (so the period immediately following the intermission).

I1D	Instances	SV	SH	AV SH	SV%
-5	2	15	18	9.0	0.833
-4	11	93	103	9.4	0.903
-3	57	533	587	10.3	0.908
-2	209	1,890	2,129	10.2	0.888
-1	530	5,031	5,560	10.5	0.905
0	924	8,978	9,897	10.7	0.907
1	530	5,625	6,153	11.6	0.914
2	209	2,164	2,388	11.4	0.906
3	57	631	689	12.1	0.916
4	11	115	125	11.4	0.920
5	2	27	29	14.5	0.931

[TBODY] [/TBODY]

I would say that the values between -2 and 2 are somewhat credible. There does appear to be this effect after 20 minutes, if not a large one.

 

[Doctor No]

2017-18 NHL regular season data, split by the score at second intermission. Shots and saves below reflect third-period data (similar to the above).

I2D	Instances	SV	SH	AV SH	SV%
-7	1	7	9	9.0	0.778
-6	4	22	27	6.8	0.815
-5	24	199	213	8.9	0.934
-4	62	520	576	9.3	0.903
-3	140	1,034	1,153	8.2	0.897
-2	302	2,332	2,578	8.5	0.905
-1	473	3,820	4,162	8.8	0.918
0	530	4,810	5,270	9.9	0.913
1	473	4,929	5,353	11.3	0.921
2	302	3,240	3,534	11.7	0.917
3	140	1,494	1,633	11.7	0.915
4	62	611	659	10.6	0.927
5	24	237	256	10.7	0.926
6	4	29	33	8.3	0.879
7	1	3	3	3.0	1.000

[TBODY] [/TBODY]

There does appear to be a similar (and larger) effect here. -1 doesn't seem to fit the overall pattern with respect to SV%. At least for the credible range, shots/period look to follow a clear pattern.

 

[Doctor No]

One to-do is for me to adjust for team quality - for instance, stronger teams generally have higher shooting percentages (so opposing goaltenders generally have lower save percentages), and stronger teams are leading at the intermission more often than not.

Empty net goals are excluded from the above.

 

[morehockeystats]

One to-do is for me to adjust for team quality - for instance, stronger teams generally have higher shooting percentages (so opposing goaltenders generally have lower save percentages), and stronger teams are leading at the intermission more often than not.

Empty net goals are excluded from the above.

Did you see the adjacent thread where I posted the correlation graph between the Saves and SVP?

 

[Doctor No]

Did you see the adjacent thread where I posted the correlation graph between the Saves and SVP?

Yes - it's interesting and matches loosely the numbers I've posted previously (once adjusting for opponent strength).

Score effects is one of the reasons and this thread is an attempt to quantify that.