tag:blogger.com,1999:blog-31545676.post2883008539707816050..comments2019-07-12T10:02:52.556-04:00Comments on Sabermetric Research: A flawed argument that marginal offense and defense have equal valuePhil Birnbaumhttp://www.blogger.com/profile/03800617749001032996noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-31545676.post-18628437558606563352018-12-01T08:20:02.331-05:002018-12-01T08:20:02.331-05:00A different argument
Win probability is zero sum....A different argument<br /><br />Win probability is zero sum. Any gains or losses to the own team exactly offset losses or gains to the other team. Since we could be performing this analysis from either perspective, the values must be equal.<br /><br />This breaks down when you have knowledge of the team,dpending on your assumptions. For instance, every team scoring a fixed amount more (each team gets x more runs) benefits below average teams, at the expense of above average teams (scoring a fixed amount less has the opposite results) . However, league wide scoring a % more or less does not affect the status quo in your model.<br /><br />If you want to answer for a specific team, will 1 run of offense or defense help more, that goes back to the question of if win by 1 or lose by 1 is more probable. The answer to that depends on if the team is better or worse than average. Is increasing or decreasing the variance good? Depends if the team is already worse or better than average respectively.Dan Rnoreply@blogger.comtag:blogger.com,1999:blog-31545676.post-42975438677884222642018-11-30T15:45:03.571-05:002018-11-30T15:45:03.571-05:00Agreed, as far as that goes. But the method also ...Agreed, as far as that goes. But the method also fails in sports where shutouts are basically non-existent. Imagine NBA, but where the FG% runs around 35% instead of 50%. You wouldn't have shutouts, but the argument still fails.<br /><br />In the real NBA, where FG% is around 50%, my answer doesn't work. Poisson is for "rare events" and 50% is not rare. So that's another hint, I guess.<br /><br />I guess, technically, the shutout argument is a valid answer, because a single counterexample is enough to disprove an hypothesis. But there's a more general argument that applies to non-shutout sports too.Phil Birnbaumhttps://www.blogger.com/profile/03800617749001032996noreply@blogger.comtag:blogger.com,1999:blog-31545676.post-24447433259897406622018-11-30T08:45:37.282-05:002018-11-30T08:45:37.282-05:00OK... "You pick a random game, and add on a r...OK... "You pick a random game, and add on a run, and see if that changes the result." You can do that to any game with equal probability. However, if you pick a random game and subtract a run, you can only do that in games where at least one run is allowed. Some games are shutouts and you can't subtract a run from those. So the random game must be one of the other non-shutout games. So in a given game that's not a shutout, the expected value of the added run is 1/162, whereas the expected value of the run saved is 1/(162 - ShO). Slightly greater. The shutout games are wins anyway and not affected by the added or subtracted run.Scott Segrinhttps://www.blogger.com/profile/17707976016425293072noreply@blogger.comtag:blogger.com,1999:blog-31545676.post-5295875213204436412018-11-29T11:41:30.672-05:002018-11-29T11:41:30.672-05:00Matthew: You're on the right track. What you ...Matthew: You're on the right track. What you said was actually the hint I was going to give!<br /><br />Scott: I completely agree, as I wrote in the previous post -- but that doesn't explain why the wrong argument is wrong.Phil Birnbaumhttps://www.blogger.com/profile/03800617749001032996noreply@blogger.comtag:blogger.com,1999:blog-31545676.post-16702609901011583052018-11-28T12:22:51.631-05:002018-11-28T12:22:51.631-05:00The lower scoring the environment, the greater the...The lower scoring the environment, the greater the value of a run. A goal in soccer is worth more (in terms of wins) than a run in baseball, is worth more than a point in basketball. A defensive run saved moves the games toward a lower scoring environment thus increasing the value of that run, whereas an offensive run scored moves it toward a higher scoring environment, comparatively decreasing the value of the run.<br /><br />It's also evident in Pythagorean expectations:<br />100 R, 100 RA ==> 100^2 + (100^2 + 100^2) = 0.500000<br />101 R, 100 RA ==> 101^2 + (101^2 + 100^2) = 0.504975<br />100 R, 99 RA ==> 100^2 + (100^2 + 99^2) = 0.505025<br /><br />The extra run saved is worth slightly more than the extra run scored.<br />Scott Segrinhttps://www.blogger.com/profile/17707976016425293072noreply@blogger.comtag:blogger.com,1999:blog-31545676.post-67562352730064247292018-11-28T08:14:15.032-05:002018-11-28T08:14:15.032-05:00Is it the zero lower bound for runs? You can alway...Is it the zero lower bound for runs? You can always increase the number of offensive runs, but you can't hold an opponent to -1 runs.Matthew Hunthttps://www.blogger.com/profile/06759432311030656368noreply@blogger.comtag:blogger.com,1999:blog-31545676.post-22010828120878770232018-11-27T17:25:15.122-05:002018-11-27T17:25:15.122-05:00The concept of measuring impact in terms of runs i...The concept of measuring impact in terms of runs is meant to be applied to a full season, not uniformly assigned to individual games. One run is worth much less in a 10-9 game than it is in a 2-1 game. As an extreme example, let's say a team averaged allowing 1.0 runs per game. Then they improved the defense by 1.0 runs per game. Would they be expected to average allowing 0.0 runs per game (100% shutouts)? No.Anonymousnoreply@blogger.com