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#1
03-22-2007, 05:00 PM
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accuracy of PECOTA team wins
does anyone know of any studies which track how accurate projected team wins (per PECOTA) are? I saw back in 2004 Nate did a study on individual PECOTA projections vs. other projection systems, but I haven't been able to find anything like this on team wins.
I'm looking at these in contrast w/ Vegas lines, and there are some big differences. for instance... The over/under on Tampa Bay is 67, over -115. Thats 11 games less than the projected PECOTA wins. The over/under on Toronto is 86.5, while PECOTA projects 80, and the under is +105. 
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#3
03-22-2007, 05:17 PM
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Re: accuracy of PECOTA team wins
Here are last year's records and PECOTA projected records:
Team Wins Losses (Projected Wins) (Projected Losses) NYY 97 65 94 68 TOR 87 75 79 83 Bos 86 76 93 69 Bal 70 92 77 85 TB 61 101 69 93 MIN 96 66 84 78 DET 95 67 83 79 CHI 90 72 82 80 CLE 78 84 88 74 KC 62 100 61 101 Oak 93 69 93 69 LAA 89 73 81 81 TEX 80 82 80 82 SEA 78 84 77 85 NYM 97 65 88 74 PHI 85 77 86 76 ATL 79 83 85 77 FLA 78 84 71 91 WAS 71 91 70 92 STL 83 78 86 76 HOU 82 80 81 81 CIN 80 82 78 84 MIL 75 87 84 78 PIT 67 95 79 83 CHI 66 96 85 77 SD 88 74 78 84 LAD 88 74 87 75 SF 76 85 80 82 AZ 76 86 77 85 COL 76 86 74 88
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#4
03-22-2007, 05:22 PM
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Re: accuracy of PECOTA team wins
[ QUOTE ]
does anyone know of any studies which track how accurate projected team wins (per PECOTA) are? I saw back in 2004 Nate did a study on individual PECOTA projections vs. other projection systems, but I haven't been able to find anything like this on team wins. I'm looking at these in contrast w/ Vegas lines, and there are some big differences. for instance... The over/under on Tampa Bay is 67, over -115. Thats 11 games less than the projected PECOTA wins. The over/under on Toronto is 86.5, while PECOTA projects 80, and the under is +105. [/ QUOTE ] crockpot said this in a post in the SB forum: "the pecotas have a standard deviation of about 8.7 games from actual results over the past four years. i believe nate claimed a standard deviation of 9.5 games. the system has been refined over that time, so in theory the number should be a little lower, but we can't really conclude this is the case. considering a perfect system has a standard deviation of 6.3 games, that's still pretty good."
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#5
03-22-2007, 05:26 PM
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Re: accuracy of PECOTA team wins
[ QUOTE ]
[ QUOTE ] does anyone know of any studies which track how accurate projected team wins (per PECOTA) are? I saw back in 2004 Nate did a study on individual PECOTA projections vs. other projection systems, but I haven't been able to find anything like this on team wins. I'm looking at these in contrast w/ Vegas lines, and there are some big differences. for instance... The over/under on Tampa Bay is 67, over -115. Thats 11 games less than the projected PECOTA wins. The over/under on Toronto is 86.5, while PECOTA projects 80, and the under is +105. [/ QUOTE ] crockpot said this in a post in the SB forum: "the pecotas have a standard deviation of about 8.7 games from actual results over the past four years. i believe nate claimed a standard deviation of 9.5 games. the system has been refined over that time, so in theory the number should be a little lower, but we can't really conclude this is the case. considering a perfect system has a standard deviation of 6.3 games, that's still pretty good." [/ QUOTE ] tx. is a 'perfect' system off by 6.3 games b/c of luck, injuries, etc?
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#6
03-22-2007, 05:28 PM
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Re: accuracy of PECOTA team wins
[ QUOTE ]
does anyone know of any studies which track how accurate projected team wins (per PECOTA) are? I saw back in 2004 Nate did a study on individual PECOTA projections vs. other projection systems, but I haven't been able to find anything like this on team wins. I'm looking at these in contrast w/ Vegas lines, and there are some big differences. for instance... The over/under on Tampa Bay is 67, over -115. Thats 11 games less than the projected PECOTA wins. The over/under on Toronto is 86.5, while PECOTA projects 80, and the under is +105. [/ QUOTE ] I haven't read through all the way through BP 2007 yet - is it simply a kind of summation of PECOTA projections for particular players? Seems like the division might have something to do with it in the case of Tampa, though one would also think that Toronto would have a similar lowered expectation.
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#7
03-22-2007, 05:28 PM
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Re: accuracy of PECOTA team wins
[ QUOTE ]
[ QUOTE ] [ QUOTE ] does anyone know of any studies which track how accurate projected team wins (per PECOTA) are? I saw back in 2004 Nate did a study on individual PECOTA projections vs. other projection systems, but I haven't been able to find anything like this on team wins. I'm looking at these in contrast w/ Vegas lines, and there are some big differences. for instance... The over/under on Tampa Bay is 67, over -115. Thats 11 games less than the projected PECOTA wins. The over/under on Toronto is 86.5, while PECOTA projects 80, and the under is +105. [/ QUOTE ] crockpot said this in a post in the SB forum: "the pecotas have a standard deviation of about 8.7 games from actual results over the past four years. i believe nate claimed a standard deviation of 9.5 games. the system has been refined over that time, so in theory the number should be a little lower, but we can't really conclude this is the case. considering a perfect system has a standard deviation of 6.3 games, that's still pretty good." [/ QUOTE ] tx. is a 'perfect' system off by 6.3 games b/c of luck, injuries, etc? [/ QUOTE ] It's just random luck, like flipping a coin. A team that is expected to go 81-81 has a standard deviation of sqrt(162*.5*.5) = 6.3. For a team with a different expected record, it would be sqrt(162*p*(1-p)), where p is probability of winning a game.
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