xG, why it doesn't work.

Everyone can agree that good teams/players overperform vs xG and bad teams/players underperform.

When an average probability is assigned it takes no account of player quality or opposition quality.

Simple example.
Borja is given 0.15 for a chance.
Might be closer to correct for an average champs player....but he isn't.
So the real value of the chance (for Borja) might be 0.25 or better.

That's why better teams/players consistently outperform xG.....
Because the xG values assigned to better players are WRONG....

Posted By: usacanary on November 27th 2024 at 13:40:24

Message Thread

XG 2.14?! (NCFC) - Kangol Canary, Nov 27, 08:24:26
- xG, why it doesn't work. (NCFC) - usacanary, Nov 27, 13:40:24
  - It's a case study in GIGO isn't it? (n/m) (NCFC) - Cardiff Canary, Nov 27, 16:29:34
    - What garbage goes in though? (NCFC) - SimonOTBC, Nov 27, 18:44:46
      - Is it? (NCFC) - Cardiff Canary, Nov 27, 18:56:10
        
        Nope. The raw data is the outcome of shots from the same part of the pitch (NCFC) - SimonOTBC, Nov 27, 19:08:34
        
        I think we just have differing views on the quality of that data then (NCFC) - Cardiff Canary, Nov 27, 19:38:02
        
        Fair enough. (NCFC) - SimonOTBC, Nov 27, 19:46:44
        
        You are a credit to xG 🎩 (n/m) (NCFC) - SCC 28, Nov 27, 20:16:34
        
        I presume it's one part of a suite of stuff (NCFC) - Cardiff Canary, Nov 27, 19:59:51
    - The thing is there is actual proof... (NCFC) - usacanary, Nov 27, 16:56:48
      - That’s how you compare players and teams though, isn’t it? (NCFC) - APB, Nov 27, 18:31:00
  - Might as well have titled it (NCFC) - SCC 28, Nov 27, 14:12:16
    - I literally explained in detail why its wrong and this is your comeback.... (NCFC) - usacanary, Nov 27, 15:54:13
      - lol others have tried explaining to you (NCFC) - SCC 28, Nov 27, 19:17:11
        
        Who explained it to me.... (NCFC) - usacanary, Nov 27, 20:57:24
- All the nerds getting off on xg... what does it actually do? Let me (NCFC) - Pixelman, Nov 27, 10:20:27
  - clubs use it so there’s that (NCFC) - SCC 28, Nov 27, 10:30:26
    - xG is bollocks because (NCFC) - Henclrikus, Nov 27, 10:41:17
      - Presumably the stats back up the xG allocation? (NCFC) - SimonOTBC, Nov 27, 11:06:58
        
        Simon, simple question, why do better teams and players outperform xG (NCFC) - usacanary, Nov 27, 16:00:36
        
        Because xG is about the average outcome of any given scenario (NCFC) - SimonOTBC, Nov 27, 16:24:29
        
        But you are giving a better player a value which is incorrect (NCFC) - usacanary, Nov 27, 21:04:40
        
        VMT (n/m) (NCFC) - SCC 28, Nov 27, 19:18:13
        
        Glad you agree with something that is Bollocks... (n/m) (NCFC) - usacanary, Nov 27, 21:05:13
        
        To be more precise (NCFC) - Henclrikus, Nov 27, 11:52:06
        
        How do they use it? (n/m) (NCFC) - SCC 28, Nov 27, 11:54:34
        
        Thye mainly use it to justify losses....... (NCFC) - usacanary, Nov 27, 16:02:14
        
        Not seen that (n/m) (NCFC) - SCC 28, Nov 27, 19:18:42
      - You’re an xG sceptic then (n/m) (NCFC) - SCC 28, Nov 27, 10:45:50
        
        If I don't believe in Santa or the tooth fairy.... (NCFC) - usacanary, Nov 27, 13:21:31
        
        You’re a septic (n/m) (NCFC) - SCC 28, Nov 27, 13:23:02
    - But what does it do? I can see it might be helpful to clubs when (NCFC) - Pixelman, Nov 27, 10:35:59
      - When the club looks at the next game.... (NCFC) - usacanary, Nov 27, 21:08:45
      - The league table is a far more useful stat. (NCFC) - usacanary, Nov 27, 12:54:50
      - Like all stats it shouldn't be looked at in isolation. Combined with other metric over (NCFC) - The Gaffer, Nov 27, 11:00:46
        
        That's fascinating. For the clubs. But for the fan on the street it is (NCFC) - Pixelman, Nov 27, 12:33:07
        
        So why bother with any of them? (NCFC) - SCC 28, Nov 27, 13:01:57
        
        Indeed. Why bother. It adds nothing to my enjoyment or othewise knowing we had (NCFC) - Pixelman, Nov 27, 13:35:34
        
        Those are actual number we can count... (NCFC) - usacanary, Nov 27, 13:06:41
        
        Boro are a good example (NCFC) - jamesward, Nov 27, 11:48:17
        
        I'm struggling to make myself clear here. That is great for clubs but (NCFC) - Pixelman, Nov 27, 12:36:19
        
        What’s the point in discussing potential line ups and tactics? (NCFC) - SCC 28, Nov 27, 13:07:06
        
        See, now your just configrating. My point is specifically about xg. (n/m) (NCFC) - Pixelman, Nov 27, 13:38:29
        
        Mikey likes to muddy the waters while losing an argument (n/m) (NCFC) - usacanary, Nov 27, 16:04:05
        
        Blimey 15 goals in their last 3 games (NCFC) - SCC 28, Nov 27, 11:58:46
      - Just a metric for those interested in the finer details (NCFC) - SCC 28, Nov 27, 10:42:20
        
        Cricket has a few. But they are based on actuals... batting average, bowling average etc.. (NCFC) - Pixelman, Nov 27, 12:39:51
        
        These are based on a large sample of incidents (NCFC) - SCC 28, Nov 27, 13:10:47
        
        Exactly, that's what Mikey doesn't get (NCFC) - usacanary, Nov 27, 12:57:28
        
        But a reliable metric needs consistent factors (NCFC) - Henclrikus, Nov 27, 11:57:31
        
        Absolutely, but with enough data you end up with an average (n/m) (NCFC) - SimonOTBC, Nov 27, 12:28:17
        
        Not sure how infinite possibilities can create an average! (NCFC) - Henclrikus, Nov 27, 12:53:48
        
        Regularly ranting about xG (NCFC) - SCC 28, Nov 27, 13:12:15
        
        I assume this is just your subjective view? (NCFC) - Henclrikus, Nov 27, 13:28:30
        
        Well I’m not going to look for each occurrence (n/m) (NCFC) - SCC 28, Nov 27, 14:16:19
        
        EDIT - twice as difficult as Sainz's 3rd. (n/m) (NCFC) - Henclrikus, Nov 27, 12:55:54
        
        Unforced errors can be pretty subjective (n/m) (NCFC) - SCC 28, Nov 27, 12:18:46
        
        That's why it's just a guide (NCFC) - jamesward, Nov 27, 12:06:33
        
        But people treat it as an arbiter (NCFC) - Henclrikus, Nov 27, 12:12:46
        
        Eh? (NCFC) - SCC 28, Nov 27, 12:23:06
      - It is an indicator of the quality of chances created (NCFC) - SimonOTBC, Nov 27, 10:41:02
        
        Nobody is addressing the fact it's subjective... (NCFC) - usacanary, Nov 27, 12:51:26
        
        I don't think that's true (NCFC) - SimonOTBC, Nov 27, 15:10:58
        
        Again, answer the question..... (NCFC) - usacanary, Nov 27, 16:12:31
        
        lol amazing it’s like part of your brain doesn’t work (n/m) (NCFC) - SCC 28, Nov 27, 19:21:57
        
        It does make sense for you to be assigned the same value... (NCFC) - SimonOTBC, Nov 27, 16:32:32
        
        👍 (NCFC) - SCC 28, Nov 27, 19:23:27
        
        Again, answer the question..... (NCFC) - usacanary, Nov 27, 16:12:00
        
        Why would it be useful to ME? (n/m) (NCFC) - Pixelman, Nov 27, 12:43:03
        
        It isn’t useful to you (NCFC) - SCC 28, Nov 27, 13:08:46
        
        I think its also misleading, which is worse. (n/m) (NCFC) - usacanary, Nov 27, 16:16:05
        
        I think its also misleading, which is worse. (n/m) (NCFC) - usacanary, Nov 27, 16:14:19
- 3.23 apparently (NCFC) - Cardiff Canary, Nov 27, 08:40:05
  - Downgraded to 3.15 (NCFC) - SCC 28, Nov 27, 08:46:55
    - Makes more sense than 2! (NCFC) - Kangol Canary, Nov 27, 09:12:09
      - Go to stats on the fotmob link (NCFC) - SCC 28, Nov 27, 10:01:16
    - Basically it’s a load of shite then? (n/m) (NCFC) - Adster, Nov 27, 09:09:31
      - No (n/m) (NCFC) - SCC 28, Nov 27, 09:14:55
        
        We scored 6 and missed a load of sitters, HTH (n/m) (NCFC) - Adster, Nov 27, 09:16:04
        
        You’re very harsh on our players (NCFC) - SCC 28, Nov 27, 09:25:43
        
        Yep (NCFC) - SimonOTBC, Nov 27, 09:34:02
        
        Surely Crnac’s header was very high (NCFC) - jamesward, Nov 27, 09:45:26
        
        0.49 (NCFC) - SCC 28, Nov 27, 10:03:08
        
        Hmm (n/m) (NCFC) - jamesward, Nov 27, 10:56:34
        
        That was 0.51 (NCFC) - SCC 28, Nov 27, 09:45:21
        
        The main thing xG shows me is that fans massively overestimate the likelihood of scoring (n/m) (NCFC) - SimonOTBC, Nov 27, 11:19:01
        
        xG massively underestimates good teams (NCFC) - usacanary, Nov 27, 13:04:18
        
        Painful (n/m) (NCFC) - SCC 28, Nov 27, 14:13:08
        
        Again, no answer to why I am wrong....thats painful to watch... (n/m) (NCFC) - usacanary, Nov 27, 16:05:31
        
        Yep and get easily wound up by what others (NCFC) - SCC 28, Nov 27, 13:03:01
        
        says others are "easily wound up" Lolzers (n/m) (NCFC) - Henclrikus, Nov 27, 13:29:40
        
        I do (n/m) (NCFC) - SCC 28, Nov 27, 14:13:26

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