Not to worry; this won't last says Myrtle

[corporatejay]

Originally Posted by Street Pharmacist

No, it's corsi minus shots blocked. It includes missed shots. May seem weird at first, but it's meant to correct corsi as shot blocking is a skill and not random

Right. But all its doing is using shots at opposing goal minus shots at your goal.

It's just shot differential but using blocked, posts and shots that miss the net.

fenwick just uses shots at net.

My point is. Like someone mentioned above with on base percentage being more I,portent than batting average. A shot that misses the net is still important and sometimes a better indicator of pressure than a dribbler from center ice that hits the goalies pad.

[Street Pharmacist]

Originally Posted by corporatejay

Right. But all its doing is using shots at opposing goal minus shots at your goal.

It's just shot differential but using blocked, posts and shots that miss the net.

fenwick just uses shots at net.

My point is. Like someone mentioned above with on base percentage being more I,portent than batting average. A shot that misses the net is still important and sometimes a better indicator of pressure than a dribbler from center ice that hits the goalies pad.

Yes, but I'm not sure what your getting at here.

Corsi = all picks directed at net full stop
Fenwick = all picks directed at net minus the ones blocked

I don't understand the point of Fenwick.
As in, Ok you got dominated but it's fine because you blocked a lot of shots? You still got dominated

[corporatejay]

Originally Posted by Street Pharmacist

Yes, but I'm not sure what your getting at here.

Corsi = all picks directed at net full stop
Fenwick = all picks directed at net minus the ones blocked

I don't understand the point of Fenwick.
As in, Ok you got dominated but it's fine because you blocked a lot of shots? You still got dominated

I'm trying to learn about fancy stats so I'm asking questions.

Why would people fight these numbers. If the flames get badly outshot all season it stands to reason that eventually their goalies will regress to the mean and they'll start losing games.

[Frequitude]

Corporatejay's just saying, "well that makes a lot of sense" and paralleling it to the hits -> on base % transition. Spot on.

[TheDebaser]

Originally Posted by Street Pharmacist

Yes, but I'm not sure what your getting at here.

Corsi = all picks directed at net full stop
Fenwick = all picks directed at net minus the ones blocked

I don't understand the point of Fenwick.
As in, Ok you got dominated but it's fine because you blocked a lot of shots? You still got dominated

They're two different concepts. You have to understand that when people are making these stats they're trying to model the game, they're not gods gift to hockey.

Corsi is an attempt to easily make a reliable possession stat out of readily available data, since shot attempts are readily available and have been shown to strongly correlate with possession time. As its critics will be quick to tell you, it carries no information about shot quality whatsoever. Corsi is a stat that tells you which team is carrying play, not necessarily which team is more likely to score.

Unfortunately, figuring out which team is more likely to score is what's important when you want to make a good educated guess about which team is more likely to win the hockey game. No one has figured out how to do that yet, but one way people are trying to get there is by trying to establish a model for how hockey works. In this model shot attempts generally follow a normal distribution, so, with enough samples, for every bad shot on goal there will generally be a good shot on goal centered around a mean-quality shot. (I haven't explained that too well, but the statistical foundation is solid. If you want to learn more check out some normal distribution videos on youtube.) Over a large enough sample size a teams shooting percentage will approach the true percent-chance that any given shot will be a goal. It makes sense to discount blocked shots in this model because any shot that is blocked will not become a chance to score. So if a team has 20 unblocked shots and is shooting at 10%, Fenwick would predict that the bell curve for goals-for for such a game would be centered around 2 and have some standard deviation.

Basically statisticians are trying to simplify hockey down to a game similar to this: Imagine if for every unblocked shot in a game you and an opponent rolled a die, and every time you rolled a one you scored a point. If you were rolling 12 times and got 5 points, while your opponent rolled 18 times and got 4 points, he would lose, but he would be right in saying that your point production is unsustainable.

My issue with analytics right now is that I think Fenwick is just a really noisy stat and hockey is practically just a little too chaotic to be modeled the way it is being modeled. The general concept isn't completely meritless though.

As for PDO, unfortunately the stat does make some sense, although it is hardly to be taken as gospel. In the above "Dice roll" analogy, a high pdo is like a number that shows how often you have been rolling ones. If you've been rolling ones half the time, with enough repetitions you will regress back to rolling ones 1/6th of the time. (Damn you Law of Large Numbers!) In reality I don't think PDO is the best stat because A) some goaltenders are better than others and can sustain higher save percentages for long periods of time,B) some teams are able to convert their chances and make chances better than others and C) some teams are able to play defense in a way that doesn't allow quality shots on goal as often as other teams. Teams that are good in those three areas will have high PDO's that are completely sustainable.

On the flipside, some teams really are just getting lucky. There's definitely some grey area there.

So basically this advanced stats stuff is not complete garbage, but it is definitely not gospel either.

[EldrickOnIce]

Exactly: data that is readily available.
This is not some advanced metric. Former Sabres goalie coach Jim Corsi invented this stat solely to help determine whether to start a goalie in back to back games. The idea being that shots on goal was not good enough. A goalie had to prepare for every shot at the net, so in a game where he only faced 20 shots (a light workload) there might have been 50 shots at goal... And he would be tired.
Nothing advanced in any way, but a great metric for goalie workload.
Stats guts then looked at it and determined that it did a decent job of modeling the game.

But nothing advanced about any of it. Simply good, common sense. If your team corsi is 40, you are getting out shot 30-20 every game, and will likely lose more than you win. Simple stuff really

[Resolute 14]

Originally Posted by Street Pharmacist

Yes, but I'm not sure what your getting at here.

Corsi = all picks directed at net full stop
Fenwick = all picks directed at net minus the ones blocked

I don't understand the point of Fenwick.
As in, Ok you got dominated but it's fine because you blocked a lot of shots? You still got dominated

Fenwick removes blocked shots on the theory that blocking is a skill rather than a random event. One needs only to watch Lance Bouma or remember Stephane Yelle to agree. Either way, if you are getting your head bashed in in terms of possession, you are likely going to be drowning in both Corsi and Fenwick.

[Kaine]

I remember when people just watched hockey.

[EldrickOnIce]

Originally Posted by Kaine

I remember when people just watched hockey.

And if you never waited and waited for the Tuesday paper with NHL stats from the previous week, it's only because that was before your time.
It's simply the evolution of sports information

[corporatejay]

Originally Posted by Frequitude

Corporatejay's just saying, "well that makes a lot of sense" and paralleling it to the hits -> on base % transition. Spot on.

Yes, thanks. I was typing that in bed last night on my phone so I probably wasn't being very articulate.

These aren't invented data points or metrics. They are fairly reliable and you could argue less subjective than shots on goal.

[Street Pharmacist]

Originally Posted by EldrickOnIce

And if you never waited and waited for the Tuesday paper with NHL stats from the previous week, it's only because that was before your time.
It's simply the evolution of sports information

Remember when hockey pool meant the Tuesday paper, a pencil, some paper and a lot of arguing and bad math?

[Resolute 14]

Originally Posted by Kaine

I remember when people just watched hockey.

I remember when you could only talk hockey with your three best friends hanging around the playground.

[Street Pharmacist]

Originally Posted by Resolute 14

Fenwick removes blocked shots on the theory that blocking is a skill rather than a random event. One needs only to watch Lance Bouma or remember Stephane Yelle to agree. Either way, if you are getting your head bashed in in terms of possession, you are likely going to be drowning in both Corsi and Fenwick.

But why bother? While blocking shots is a skill, it's irrelevant when determining who controlled the play. I'm confused as to it's relevance. Does it correlate with winning better?

[Resolute 14]

Originally Posted by Street Pharmacist

But why bother? While blocking shots is a skill, it's irrelevant when determining who controlled the play. I'm confused as to it's relevance. Does it correlate with winning better?

Probably not. Just another way to look at things.

[Street Pharmacist]

Originally Posted by Resolute 14

Probably not. Just another way to look at things.

Just seems wierd. Like if they only counted shots from forwards because bocking passing lanes is a skill. Just seems silly

[corporatejay]

Originally Posted by Street Pharmacist

But why bother? While blocking shots is a skill, it's irrelevant when determining who controlled the play. I'm confused as to it's relevance. Does it correlate with winning better?

Fenwick just thinks that Corsi is meant to be a proxy for scoring chances, not play control per se. This is why he omits blocked shots.

My argument is basically: 1. The whole (or perhaps best) use of Corsi is to have objective figures that can be used as a proxy for scoring chances (what else are you using it for?).

2. A shot that is blocked is either a) not a scoring chance at all, or b) on average from a worse scoring area than shots/posts/missed shots.


He wrote that in 2007, and I feel like 7 years later there are a lot more blocked shots, even those from the slot, so I'm not sure how useful argument 2 is anymore.

[EldrickOnIce]

Originally Posted by Street Pharmacist

Remember when hockey pool meant the Tuesday paper, a pencil, some paper and a lot of arguing and bad math?

Haha vividly lol

[Enoch Root]

Originally Posted by Street Pharmacist

But why bother? While blocking shots is a skill, it's irrelevant when determining who controlled the play. I'm confused as to it's relevance. Does it correlate with winning better?

It's not irrelevant though.

Shot blocking has become a defensive strategy. If both teams make 60 shot attempts and one team blocks 20 of them while the other team doesn't, the team that blocked 20 is in a good position to have given up fewer goals.

This is a situation where the game has changed. 20 years ago (probably even 10), a blocked shot would be considered essentially identical to a shot that missed the net - in both cases, it was simply a failed shot but if you kept doing it, presumably you would eventually hit the net or get it by the block and be successful.

But in today's NHL, blocking shots has become more and more of a defensive strategy. The Flames, as an example, collapse to the centre of the ice, allowing the other team to maintain possession at the perimeter. The strategy is to keep shots to the outside and to block as many as possible, reducing scoring chances that way.

It is simply a different way to play defense.

And the stats, as designed, haven't adjusted to it.

If all teams employed the strategy equally, it would be fine and the numbers wouldn't get skewed. But when teams are playing different strategies, and one strategy freely allows for more shots against, the stats as they are, will be miss-leading.

Having said that, the difference would be unlikely to be really massive - the question is: how significant is the difference?

[Enoch Root]

There seems to be a theme in the last number of posts suggesting that those on the -anti advanced stats' side of the argument don't understand the stats or think they are flawed.

While there are some valid arguments that there are some marginal flaws, that is not the problem at all. The stats are fine. What they are quantifying is fine.

The primary problem is that the people wielding them often don't understand how to utilize stats for analysis. Too often it is a case of: here's a stat showing an imbalance, therefore this is going to happen.

Doesn't work that way.

[_Q_]

Originally Posted by Enoch Root

There seems to be a theme in the last number of posts suggesting that those on the -anti advanced stats' side of the argument don't understand the stats or think they are flawed.

While there are some valid arguments that there are some marginal flaws, that is not the problem at all. The stats are fine. What they are quantifying is fine.

The primary problem is that the people wielding them often don't understand how to utilize stats for analysis. Too often it is a case of: here's a stat showing an imbalance, therefore this is going to happen.

Doesn't work that way.

I agree with this for the most part but I have to disagree that what's being quantified is accurate with regards to Corsi or Fenwick quantifying "possession". Those two stats quantify shot attempts and not possession, full stop. Sure, they can be used as a model to help understand possession, but they are not able to measure anything other than shot attempts. The only way to measure possession right now is to get a stop watch and time the number of minutes a team has possession of the puck during the game (and I'm sure some teams have employed that strategy).

For example, say you are trying to figure out how rich a group of 1000 people is, but for some reason, they don't want to tell you how much money they make. You find a correlation between wealth and the price of vehicle they drive. So you create a model in which you figure out what type of vehicle each one of those 1000 people drive and figure out where each one of them stands in terms of wealth. Sure it might make sense and it might be an accurate model for 95‰ of the population, but if one rich guy is happy driving a 1995 Accord or one not so rich guy puts all his money into a brand new Benz, then that throws everything out of whack.

Similarly, if a team employs a strategy in which they don't try to limit shot attempts, but try to limit scoring chances instead and instead of randomly firing pucks on net they hold on to the puck a bit longer in order to get into good scoring lanes, then it throws the whole corsi/Fenwick possession model out of whack as well.

In the vehicle wealth model, you can't say you're measuring wealth. By measuring the price of the vehicle you're measuring vehicle price and interpreting the data to figure figure out wealth.

Similarly, corsi/Fenwick aren't measuring possession no matter which way someone tries to spin it.