Aug 072012

I am a firm believer in shot quality.  I have probably looked at it a dozen different ways and it seems pretty clear to me that it exists and yet there are still a lot of doubters out there so I wanted to take yet another opportunity to show that show quality exists and give an opportunity for the shot quality deniers to tell me what I am doing wrong if I am doing something wrong.

First lets start off with a definition of shot quality to make it clear what I am referring to.  Some people refer to shot quality as shot location (i.e. shot distance) but to me shot quality is even more basic than that.  For me for shot quality to exist it must only be shown that one group of shots is more difficult to save than another group of shots after taking into account game situation (i.e. 5v5 vs PK vs PP), score effects, and any factors that might affect shot quality.

So, let me take 2 groups of shots.

Group 1:  All the shots taken by the Penguins when Sidney Crosby is on the ice during 5v5 close zone start adjusted  (eliminating first 10 seconds after a face off) play over the past 5 seasons.

Group 2:  All the shots taken by the Penguins when Tyler Kennedy is on the ice during 5v5 close zone start adjusted  (eliminating first 10 seconds after a face off) play over the past 5 seasons.

I am using 5v5 close situations so that eliminates any situation and score effects that might influence shot quality.  I am also eliminating the shots within 10 seconds of a face off because they have been shown to be far easier shots to save and we wouldn’t want to disadvantage one above groups if it had a disproportionate number of shots immediately after a face off.

Also, since both players have played the past 5 seasons with the same team it eliminates any scorekeeper bias with their shot counts since both have played behind the same score keepers.  So, let’s look at the numbers.

Group GF SF Sh% Chance
Group 1 (Crosby) 150 1292 11.61% 1.65%
Group 2 (Kennedy) 92 1166 7.89% 1.23%
Totals 242 2458 9.85%

The Sh% column looks pretty telling on its own, but the Chance column says it all.  The Chance column is the liklihood that the groups shooting percentage could be what it was based on luck alone using a binomial distribution with a real shooting percentage of 9.85%.  In short, it is very unlikely that Crosby and Kennedy would have those on-ice shooting percentages based on luck alone.

Truth be told, for these two players score effects would have very little effect on their relative stats since they played almost equal time leading as trailing so we could increase our sample size fairly significantly if we looked at 5 year zone start adjusted 5v5 shots and goals.

Group GF SF Sh% Chance
Group 1 (Crosby) 243 1964 12.37% 0.17%
Group 2 (Kennedy) 150 1837 8.17% 0.09%
Totals 393 3801 10.34%

So essentially there is no chance that that happens based on luck alone.  Shot quality of some sort is a factor.  There is definitely show shot quality skill/talent factoring into the equation.

So my question to shot quality deniers is as follows.  If the above is not evidence that shot quality exists, why not, and if it is evidence of shot quality, why are you still in denial that shot quality exists?