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-   -   Non-traditional metrics: PDO (http://hfboards.hockeysfuture.com/showthread.php?t=1240933)

kmad 08-02-2012 09:04 PM

Non-traditional metrics: PDO
 
http://www.fearthefin.com/2012/8/2/3...s-glossary-pdo

Quote:

PDO is the sum of a team's 5v5 shooting percentage (the number of goals they score divided by the number of shots on goal they generate) and their 5v5 save percentage (the number of shots their goalies stop divided by the number of shots on goal they allow). In order to give us a nice whole number, after adding a team's 5v5 SH% and 5v5 SV%, we usually multiply the result by 10. For example, last season the Sharks posted a 7.0% 5v5 shooting percentage and a 92.6% 5v5 save percentage. 10*(7+92.6) equals 996, meaning the Sharks had a 5v5 PDO of 996 during the 2011-12 season. Since every shot that hits the net is either a goal or a save, the combined (or average) PDO of all NHL teams is 1000.
Thoughts?

Iain Fyffe 08-02-2012 09:18 PM

My only comment at the moment is about the unfortunate tendency to give new advanced stats impenetrable names. There's no reason at all for this to be called PDO. It's not descriptive in the least; it's not even an attempt to be descriptive. The same goes for Corsi and Fenwick. I don't want to believe it's an attempt at exclusiveness, where a thing is called something non-descriptive so that only those in the know will understand it. But sometimes I do wonder. There's any number of things I developed over the years that I could have just called "the Fyffe ratio" or what have you, but I use descriptive terms, because the purpose of new stats is to explain and clarify things, not to obfuscate them.

Sorry, that's presumably not the type of thought you were looking for.

svat 08-02-2012 09:27 PM

Quote:

Originally Posted by Iain Fyffe (Post 53235231)
My only comment at the moment is about the unfortunate tendency to give new advanced stats impenetrable names. There's no reason at all for this to be called PDO. It's not descriptive in the least; it's not even an attempt to be descriptive. The same goes for Corsi and Fenwick. I don't want to believe it's an attempt at exclusiveness, where a thing is called something non-descriptive so that only those in the know will understand it. But sometimes I do wonder. There's any number of things I developed over the years that I could have just called "the Fyffe ratio" or what have you, but I use descriptive terms, because the purpose of new stats is to explain and clarify things, not to obfuscate them.

Sorry, that's presumably not the type of thought you were looking for.

Fully agreed. The first time I was introduced to PDO, the explanation I read was ridiculously convoluted. After reading a blog post on I think one of the nation sites, it was much more easily explained. The name not relating to anything telling you about regression towards the mean in terms of percentages doesn't help at all.

More on topic, it's a great stat. While there are exceptions, and we shouldn't be deciding that Crosby will inevitably come back down to earth when he puts up a high PDO, he and a few others are the exception. I like it more on the team level tbh, just because of how it explains so many things that tired old narratives that fans use are wrong (see Minnesota).

Czech Your Math 08-02-2012 09:40 PM

How is this better, or even as good as, ES GF/GA ratio or differential (i.e. plus-minus)?

It's "the most useful stat" because it regresses to the mean?

I'd say it's more like "most useless stat."

GKJ 08-02-2012 10:03 PM

Aside from extreme cases, I think PDO is best used as a team metric.

Czech Your Math 08-02-2012 10:33 PM

Quote:

Originally Posted by svat (Post 53235511)
More on topic, it's a great stat. While there are exceptions, and we shouldn't be deciding that Crosby will inevitably come back down to earth when he puts up a high PDO, he and a few others are the exception. I like it more on the team level tbh, just because of how it explains so many things that tired old narratives that fans use are wrong (see Minnesota).

Isn't it essentially a "luck indicator" that also assumes shot quality remains constant amongst teams and between time periods?

Iain Fyffe 08-02-2012 10:45 PM

Quote:

Originally Posted by Czech Your Math (Post 53237669)
Isn't it essentially a "luck indicator" that also assumes shot quality remains constant amongst teams and between time periods?

I don't think it assumes this; I think the research demonstrates that this is largely true.

svat 08-03-2012 12:03 AM

Quote:

Originally Posted by Czech Your Math (Post 53235947)
How is this better, or even as good as, ES GF/GA ratio or differential (i.e. plus-minus)?

It's "the most useful stat" because it regresses to the mean?

I'd say it's more like "most useless stat."

Teams have shown that they cannot sustain very high PDO's over a season (can't remember the article I found, but it basically showed no team demonstrated an ability to shoot too high over the mean for even half a season [with exceptions of course, i.e the preds this year, terrible team that rode percentages the whole year and special teams]). It is very important because it tells you who is playing well enough to sustain their success and who is just getting hot for a bit. Goal differential is of course very important, but in conjunction with PDO, it really weeds out who SHOULD continue their success and who should fall back down.

svat 08-03-2012 12:07 AM

Quote:

Originally Posted by GKJ (Post 53236701)
Aside from extreme cases, I think PDO is best used as a team metric.

It's useful on the individual level when it lets you know if a player is getting VERY lucky, like Chris Kelly and his 1040+ PDO this year, which is just ridiculous, and I still don't understand how Chiarelli can give him that contract considering Chiarelli is known for making use of advanced stats.

Hynh 08-03-2012 07:31 AM

PDO is a stat that is best used to anger fanbases around December by telling them that their team isn't actually as good as they think they are, then watching as they become progressively more sullen as the prediction plays out.

Roke 08-03-2012 10:06 AM

Quote:

Originally Posted by svat (Post 53240173)
Teams have shown that they cannot sustain very high PDO's over a season (can't remember the article I found, but it basically showed no team demonstrated an ability to shoot too high over the mean for even half a season [with exceptions of course, i.e the preds this year, terrible team that rode percentages the whole year and special teams]). It is very important because it tells you who is playing well enough to sustain their success and who is just getting hot for a bit. Goal differential is of course very important, but in conjunction with PDO, it really weeds out who SHOULD continue their success and who should fall back down.

This was the best article I've read for explaining the regression at the team-level:
http://www.mc79hockey.com/?p=2996


Quote:

Originally Posted by Hynh (Post 53244133)
PDO is a stat that is best used to anger fanbases around December by telling them that their team isn't actually as good as they think they are, then watching as they become progressively more sullen as the prediction plays out.

Colorado, Dallas, and Minnesota have been on the cruel end of it in recent years as teams riding the high-percentages wave into a point in the season where you can get optimistic. The Leafs of last season had a similar thing go along but their hot start didn't last nearly long enough to build up much hope.

SmellOfVictory 08-03-2012 01:45 PM

Quote:

Originally Posted by Czech Your Math (Post 53235947)
How is this better, or even as good as, ES GF/GA ratio or differential (i.e. plus-minus)?

It's "the most useful stat" because it regresses to the mean?

I'd say it's more like "most useless stat."

It's best used to bring context to other numbers. e.g. if a player/team has an insanely good ES GF/GA differential but an enormous PDO then it brings the context that much of that was likely a run of good bounces rather than actually outplaying the opponent.

There are caveats that very good players on very good lines will tend to have a slightly higher PDO than average (similarly, a team with an elite goaltender will have a higher than average PDO due to skill), but given a few seasons' worth of data, trends can be worked out.

GKJ 08-05-2012 04:41 PM

Quote:

Originally Posted by svat (Post 53240259)
It's useful on the individual level when it lets you know if a player is getting VERY lucky, like Chris Kelly and his 1040+ PDO this year, which is just ridiculous, and I still don't understand how Chiarelli can give him that contract considering Chiarelli is known for making use of advanced stats.

That qualifies as 'extreme case,' as Chris Kelly led the league in PDO

Fourier 08-05-2012 06:16 PM

I'll be honest. I don't believe this statistic can be used to say much at all about an individual's play. This is really one of my big issues with many of the advanced stats. They may be able to say something about team play but tend to not be very convincing on an individual basis. An what ever value they may have when taken in proper context tends to disappear becuase too many people see them as being more isgnificant than they are.

And I may be wrong but I believe the name PDO comes form an HF poster who is also an active participant on the Oiler blogosphere.

Doctor No 08-05-2012 06:21 PM

Quote:

Originally Posted by Iain Fyffe (Post 53235231)
My only comment at the moment is about the unfortunate tendency to give new advanced stats impenetrable names. There's no reason at all for this to be called PDO. It's not descriptive in the least; it's not even an attempt to be descriptive. The same goes for Corsi and Fenwick. I don't want to believe it's an attempt at exclusiveness, where a thing is called something non-descriptive so that only those in the know will understand it. But sometimes I do wonder. There's any number of things I developed over the years that I could have just called "the Fyffe ratio" or what have you, but I use descriptive terms, because the purpose of new stats is to explain and clarify things, not to obfuscate them.

Sorry, that's presumably not the type of thought you were looking for.

I couldn't agree more about this.

If Corsi were just called "shots taken plus-minus" (or something similar) then maybe people would take it more seriously for what it is and what it isn't.

(For one thing, by its very nature it can't measure shot quality. Not that that's a bad thing - the stat is what it is. It'd be like getting upset at a pair of hockey skates because they don't protect your head.)

Strong Island 08-05-2012 07:51 PM

Quote:

Originally Posted by svat (Post 53235511)
More on topic, it's a great stat. While there are exceptions, and we shouldn't be deciding that Crosby will inevitably come back down to earth when he puts up a high PDO, he and a few others are the exception. I like it more on the team level tbh, just because of how it explains so many things that tired old narratives that fans use are wrong (see Minnesota).

That's the main reason I like it too. It's simple and great to use on a team wide level. I would agree with the common sentiment in this thread that it isn't as good at the individual level for obvious reasons. However it could certainly be useful for in-depth studies on individual players if you use it alongside other metrics.

MasterofGrond 08-06-2012 01:50 PM

Relatively limited value as an individual metric but quite useful as a team metric, in my opinion.

SmellOfVictory 08-07-2012 05:17 PM

I'm curious as to why people think it's so limited as an individual metric.

Fourier 08-08-2012 10:25 AM

Quote:

Originally Posted by SmellOfVictory (Post 53363717)
I'm curious as to why people think it's so limited as an individual metric.

Personally I do not believe the statistic does much to isolate the individual.

A bit OT, PDO is one of the "regression to the mean" type stats that I think are often very much misused. Here for example is Derek Zona's take on what the numbers say about Jordan Eberle...

Quote:

It's all been said already by Scott, Tyler myself and others. He got pillow soft minutes, shot the lights out, his teammates shot the lights out and his IPP was crazy. If he gets tougher minutes, has regression in his shooting percentage, his on-ice shooting percentage and his IPP, he's going to drop 25-30 points. I'm not saying all of them will regress at once, but it's not unlikely either.
http://www.coppernblue.com/2012/8/7/...-jordan-eberle

What we are being told is that Jordan Eberle's previous season was really primarily a product of luck, and the suggestion above is that he is a 45-50 point player. In my opinion this is simply a ridiculous conclussion for anyone who is supposedly a fan of the Oilers and certainly for anyone who has watched Jordan Eberle play. (And the same goes for those teammates of his who I guess also got lucky.)

While PDO is not explicitly quoted it's use, or should I say misues, tends to lead similar types of statements.

Czech Your Math 08-08-2012 08:00 PM

I've looked at this a bit more and I still don't get it.

First, the statement of it being "the single most useful statistic in hockey" is so flabbergasting, I honestly don't know how to even begin.

Second, the basis of it is said to be that both SV% and shooting % are "primarily luck-driven." Really? Maybe in the short term, but over any longer period, that's clearly false IMO. SV% is considered as or more important than any statistic for judging goalie performance by those that specialize in this. Shooting % isn't one of my favorite stats, but to say it's primarily luck-driven also doesn't seem correct IMO.

There's a graph on the link in the OP for this thread, but I'm not sure what to conclude from it. If it shows regression to the mean over time, why does it start rising at some point, plateau (2000-2500 shots) and then fall (2500-3000 shots)? Shouldn't it continue rising as the sample size increases?

I don't know where to find all the relevant team 5v5 data (shooting%, SV%, shots F-A, etc.), so I'm looking at overall data here. Here are the examples given in the link to PDO:

1) 2012 Minnesota- This seems to be the featured keystone example in the linked article and the whole basis of this example is that Minn's SV% was an unreasonably high .944 as of Dec. 11. This does seem quite high, but am not sure how 5v5 SV% varies from overall SV%, so not sure how high the variation was. What else was happening besides "luck regressing to the mean"?:

A) The top 2 Minn. goalies each had .932 overall SV%s as of Dec. 11. It seems odd that they would have basically identical SV%s given that this is supposedly all driven by luck.

B) Backstrom's .932 overall SV% to that point was .018 better than the year-end league avg. of .914. In his first 3 seasons ('07-'09) his overall SV%s were .024, .012 and .015 better than league avg. How is .018 better than league avg. so different from some of his previous performances?

C) Backstrom was the starter or at least the biggest part of the tandem/trio. He misses large chunks of games in both January and March. This means he may have been rusty, still partially injured, or (looking at the data) possibly overworked upon his return. This also means the remaining goalie(s) may have been overworked during his absence.

D) Through Dec. 11, excluding SO goals, Minn. averaged 2.47 GPG, while after Dec. 11 they averaged 1.77 GPG.

E) They finished with an overall SV% + S% of 995, so they must have been very unlucky the last 2/3 of the season, right?

Attributing Minnesota's collapse purely to "luck regressing to the mean" seems quite simplistic and likely incorrect IMO. I'm going to quickly address the other examples, since they were basically glossed over in the linked article, and after the featured example, my impression of this metric, or at least the article supporting it, went from skeptical to "does not pass inspection."

2) 2012 St. Louis- They were supposedly unlucky at the start of the season before luck regressed to the mean. Maybe so, but according their overall SV% + S% was the fourth highest in the league at 1014, even with such an "unlucky" start. How does a stat, that supposedly regresses to the mean, fluctuate so wildly that it goes from unlucky to not just normal but very lucky? How does one draw valid conclusions from such a stat?

3) 2011 Dallas & New Jersey- Again, Dallas was supposedly very lucky at the start and New Jersey very unlucky. Yet Dallas finished 7th or 8th in overall SV% + S% at 1012 and New Jersey finished last at 983. I don't see where their luck regressed to the mean, at least enough to explain their different fates.

4) 2010 Colorado- Once again, Colorado was supposedly lucky at the start, but finished second with an overall SV% + S% of 1021. I don't see where their luck regressed to the mean, at least enough to explain their fall.

Other team examples of overall SV% + S% (which is supposedly random and driven by luck, at least the 5v5 version):

Vancouver was 1018, 1019, 1026 and 1019 the last 4 seasons.
Boston was 1036, 998, 1023 and 1019 the last 4 seasons.
Nashville was 1016 and 1024 the last 2 seasons.
Phoenix was 1006, 1010, and 1013 the last 3 seasons.
Rangers were 1006, 1013 and 1019 the last 3 seasons.

Islanders were 986, 989, 998, and 984 the last 4 seasons.
Columbus was 999, 994, 984, and 984 the last 4 seasons.
Toronto was 981 and 975, before improving to 997 and 998.
Edmonton was 989 and 990 before improving to 1007.

To me, it's a mix of competing factors:

- high shooting skill
- teams waiting for high quality shots
- teams forcing low quality shots
- great goaltending

vs. the opposites of each of those vs. luck

It's a patchwork of various factors, which are often muddled by a large dose of luck. That makes its use severely limited as either a measure of total skill by goalies/shooters on a team, or as measure of luck. The individual version is even more prone to fluctuation and so basically even more useless. Why would I use the goalie's SV% over a very small sample as half of a metric for an individual skater, whether it's supposed to indicate the skater's skill or luck?

I think if one used it on a team basis and compared it to how that team did in the past, it might indicate that either the team is getting better/worse or luckier/unluckier. However, as I said in a previous post, why wouldn't one just use GF/GA or some such metric that is at least as easy to find and is more directly indicative of performance?

seventieslord 08-09-2012 02:30 AM

Quote:

Second, the basis of it is said to be that both SV% and shooting % are "primarily luck-driven." Really? Maybe in the short term, but over any longer period, that's clearly false IMO. SV% is considered as or more important than any statistic for judging goalie performance by those that specialize in this. Shooting % isn't one of my favorite stats, but to say it's primarily luck-driven also doesn't seem correct IMO.
No, it's not necessarily luck-driven for the players doing the shooting and making the saves, but it does create a luck variable in +/- for everyone else on the ice. Goalie stands on his head for a shift, players who otherwise deserved a plus don't get one. Goalie lets in a stinker, players who didn't get a minus all get one, not to mention, the other team gets pluses they don't deserve.

PDO shows who was the beneficiary of more "puck luck" throughout the season. The swings between some players are surprising, and yes, they do appear to be fairly random. All other factors being equal, two players could have CORSIs on opposite ends of the spectrum but end up with the same +/- due to just PDO. One badly outperformed the other one but +/- doesn't catch it. CORSI does, and PDO explains the disconnect between CORSI and PDO. Their CORSI scores are very indicative of future performance, while the PDOs are random, so the player with the high CORSI is the much better bet going forward, when the luck starts to balance out or regress to the mean in the long term.

Fourier 08-09-2012 06:20 AM

Quote:

Originally Posted by Czech Your Math (Post 53399873)
I've looked at this a bit more and I still don't get it.

First, the statement of it being "the single most useful statistic in hockey" is so flabbergasting, I honestly don't know how to even begin.

Second, the basis of it is said to be that both SV% and shooting % are "primarily luck-driven." Really? Maybe in the short term, but over any longer period, that's clearly false IMO. SV% is considered as or more important than any statistic for judging goalie performance by those that specialize in this. Shooting % isn't one of my favorite stats, but to say it's primarily luck-driven also doesn't seem correct IMO.

There's a graph on the link in the OP for this thread, but I'm not sure what to conclude from it. If it shows regression to the mean over time, why does it start rising at some point, plateau (2000-2500 shots) and then fall (2500-3000 shots)? Shouldn't it continue rising as the sample size increases?

I don't know where to find all the relevant team 5v5 data (shooting%, SV%, shots F-A, etc.), so I'm looking at overall data here. Here are the examples given in the link to PDO:

1) 2012 Minnesota- This seems to be the featured keystone example in the linked article and the whole basis of this example is that Minn's SV% was an unreasonably high .944 as of Dec. 11. This does seem quite high, but am not sure how 5v5 SV% varies from overall SV%, so not sure how high the variation was. What else was happening besides "luck regressing to the mean"?:

A) The top 2 Minn. goalies each had .932 overall SV%s as of Dec. 11. It seems odd that they would have basically identical SV%s given that this is supposedly all driven by luck.

B) Backstrom's .932 overall SV% to that point was .018 better than the year-end league avg. of .914. In his first 3 seasons ('07-'09) his overall SV%s were .024, .012 and .015 better than league avg. How is .018 better than league avg. so different from some of his previous performances?

C) Backstrom was the starter or at least the biggest part of the tandem/trio. He misses large chunks of games in both January and March. This means he may have been rusty, still partially injured, or (looking at the data) possibly overworked upon his return. This also means the remaining goalie(s) may have been overworked during his absence.

D) Through Dec. 11, excluding SO goals, Minn. averaged 2.47 GPG, while after Dec. 11 they averaged 1.77 GPG.

E) They finished with an overall SV% + S% of 995, so they must have been very unlucky the last 2/3 of the season, right?

Attributing Minnesota's collapse purely to "luck regressing to the mean" seems quite simplistic and likely incorrect IMO. I'm going to quickly address the other examples, since they were basically glossed over in the linked article, and after the featured example, my impression of this metric, or at least the article supporting it, went from skeptical to "does not pass inspection."

2) 2012 St. Louis- They were supposedly unlucky at the start of the season before luck regressed to the mean. Maybe so, but according their overall SV% + S% was the fourth highest in the league at 1014, even with such an "unlucky" start. How does a stat, that supposedly regresses to the mean, fluctuate so wildly that it goes from unlucky to not just normal but very lucky? How does one draw valid conclusions from such a stat?

3) 2011 Dallas & New Jersey- Again, Dallas was supposedly very lucky at the start and New Jersey very unlucky. Yet Dallas finished 7th or 8th in overall SV% + S% at 1012 and New Jersey finished last at 983. I don't see where their luck regressed to the mean, at least enough to explain their different fates.

4) 2010 Colorado- Once again, Colorado was supposedly lucky at the start, but finished second with an overall SV% + S% of 1021. I don't see where their luck regressed to the mean, at least enough to explain their fall.

Other team examples of overall SV% + S% (which is supposedly random and driven by luck, at least the 5v5 version):

Vancouver was 1018, 1019, 1026 and 1019 the last 4 seasons.
Boston was 1036, 998, 1023 and 1019 the last 4 seasons.
Nashville was 1016 and 1024 the last 2 seasons.
Phoenix was 1006, 1010, and 1013 the last 3 seasons.
Rangers were 1006, 1013 and 1019 the last 3 seasons.

Islanders were 986, 989, 998, and 984 the last 4 seasons.
Columbus was 999, 994, 984, and 984 the last 4 seasons.
Toronto was 981 and 975, before improving to 997 and 998.
Edmonton was 989 and 990 before improving to 1007.

To me, it's a mix of competing factors:

- high shooting skill
- teams waiting for high quality shots
- teams forcing low quality shots
- great goaltending

vs. the opposites of each of those vs. luck

It's a patchwork of various factors, which are often muddled by a large dose of luck. That makes its use severely limited as either a measure of total skill by goalies/shooters on a team, or as measure of luck. The individual version is even more prone to fluctuation and so basically even more useless. Why would I use the goalie's SV% over a very small sample as half of a metric for an individual skater, whether it's supposed to indicate the skater's skill or luck?

I think if one used it on a team basis and compared it to how that team did in the past, it might indicate that either the team is getting better/worse or luckier/unluckier. However, as I said in a previous post, why wouldn't one just use GF/GA or some such metric that is at least as easy to find and is more directly indicative of performance?

Excellent post.

mindmasher 08-09-2012 11:50 AM

Quote:

Originally Posted by Fourier (Post 53381697)
Personally I do not believe the statistic does much to isolate the individual.

A bit OT, PDO is one of the "regression to the mean" type stats that I think are often very much misused. Here for example is Derek Zona's take on what the numbers say about Jordan Eberle...



http://www.coppernblue.com/2012/8/7/...-jordan-eberle

What we are being told is that Jordan Eberle's previous season was really primarily a product of luck, and the suggestion above is that he is a 45-50 point player. In my opinion this is simply a ridiculous conclussion for anyone who is supposedly a fan of the Oilers and certainly for anyone who has watched Jordan Eberle play. (And the same goes for those teammates of his who I guess also got lucky.)

While PDO is not explicitly quoted it's use, or should I say misues, tends to lead similar types of statements.

Hunh? What is incorrect about his statement? I'm a huge fan of the Oilers and Eberle; I wish him the best, but it's very simple: he performed at a historically unsustainable level and it's very unlikely that he repeats it. Possible, as most things are, but unlikely.

Not even to mention you are trying to someone hold this up as an indicator of advanced statistic misuse - and I see *zero* arguments as to why this is the case. Why is this a ridiculous conclusion? Where are your arguments that his IPP and S% are sustainable and not influenced heavily by a season of good bounces. I would love to see some contrary arguments based on logic, not hand waving.

Czech Your Math 08-09-2012 11:59 AM

Quote:

Originally Posted by seventieslord (Post 53408135)
No, it's not necessarily luck-driven for the players doing the shooting and making the saves, but it does create a luck variable in +/- for everyone else on the ice. Goalie stands on his head for a shift, players who otherwise deserved a plus don't get one. Goalie lets in a stinker, players who didn't get a minus all get one, not to mention, the other team gets pluses they don't deserve.

PDO shows who was the beneficiary of more "puck luck" throughout the season. The swings between some players are surprising, and yes, they do appear to be fairly random. All other factors being equal, two players could have CORSIs on opposite ends of the spectrum but end up with the same +/- due to just PDO. One badly outperformed the other one but +/- doesn't catch it. CORSI does, and PDO explains the disconnect between CORSI and PDO. Their CORSI scores are very indicative of future performance, while the PDOs are random, so the player with the high CORSI is the much better bet going forward, when the luck starts to balance out or regress to the mean in the long term.

But who relies on simple plus-minus, esp. over a full season or less, as a supreme measure of value? At most, one might use simple +/- as a supplemental stat over a full season or more. Anyone serious would use adjusted plus-minus, preferably over multiple seasons, as one of the metrics of value. On a team level, I would use GF/GA ratio or differential. One doesn't need PDO to know that a large change will usually regress towards the previous level the following year, Bill James proved that decades ago for baseball.

I think there's too much put into stats like Corsi too. It's at least measuring something, but outshooting the opposition does not equal success. Outshoot Hasek, all you want, it might not help one bit. I think Corsi might tell you something about possession, but much less about overall effectiveness. Boston was outshot two years ago, but they won the Cup. I think they'll take the goals and leave the shots for their opponents.

mindmasher 08-09-2012 12:07 PM

Quote:

Originally Posted by Czech Your Math (Post 53399873)
However, as I said in a previous post, why wouldn't one just use GF/GA or some such metric that is at least as easy to find and is more directly indicative of performance?

No, it would not. One is a measurement of efficiency, the other of result. GF is the result of SF * S%, and GA is the result of (1 - Sv%) * SA.

As many people have stated many times in many ways using strategies firmly rooted in sound statistical reasoning, shot volume (SF/SA) is something that good teams tend to be good at.

The efficiency percentages over the long term for ALL teams tends to regress back to league averages. In other words, outliers of the efficiency percentages are not generated by the teams ability since they will always tend to head back to league averages.

So again, no GD, GF, and GA are not the same pieces of information. PDO is a lot more useful when looking at unsustainable performances.


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