andrew_gelman_stats andrew_gelman_stats-2012 andrew_gelman_stats-2012-1215 knowledge-graph by maker-knowledge-mining
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Introduction: Gur Yaari writes : Anyone who has ever watched a sports competition is familiar with expressions like “on fire”, “in the zone”, “on a roll”, “momentum” and so on. But what do these expressions really mean? In 1985 when Thomas Gilovich, Robert Vallone and Amos Tversky studied this phenomenon for the first time, they defined it as: “. . . these phrases express a belief that the performance of a player during a particular period is significantly better than expected on the basis of the player’s overall record”. Their conclusion was that what people tend to perceive as a “hot hand” is essentially a cognitive illusion caused by a misperception of random sequences. Until recently there was little, if any, evidence to rule out their conclusion. Increased computing power and new data availability from various sports now provide surprising evidence of this phenomenon, thus reigniting the debate. Yaari goes on to some studies that have found time dependence in basketball, baseball, voll
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1 Gur Yaari writes : Anyone who has ever watched a sports competition is familiar with expressions like “on fire”, “in the zone”, “on a roll”, “momentum” and so on. [sent-1, score-0.575]
2 In 1985 when Thomas Gilovich, Robert Vallone and Amos Tversky studied this phenomenon for the first time, they defined it as: “. [sent-3, score-0.202]
3 these phrases express a belief that the performance of a player during a particular period is significantly better than expected on the basis of the player’s overall record”. [sent-6, score-0.288]
4 Their conclusion was that what people tend to perceive as a “hot hand” is essentially a cognitive illusion caused by a misperception of random sequences. [sent-7, score-0.367]
5 Until recently there was little, if any, evidence to rule out their conclusion. [sent-8, score-0.072]
6 Increased computing power and new data availability from various sports now provide surprising evidence of this phenomenon, thus reigniting the debate. [sent-9, score-0.407]
7 Yaari goes on to some studies that have found time dependence in basketball, baseball, volleyball, and bowling. [sent-10, score-0.078]
8 We are not machines, and anything that can affect our expectations (for example, our success in previous tries) should affect our performance. [sent-13, score-0.408]
9 The effects I’ve seen are small, on the order of 2 percentage points (for example, the probability of a success in some sports task might be 45% if you’re “hot” and 43% otherwise). [sent-15, score-0.496]
10 Yaari presents his results in terms of p-values but I think it’s best to look at effect sizes directly in terms of probabilities. [sent-16, score-0.242]
11 Sometimes if you succeed you will stay relaxed and focused, other times you can succeed and get overconfidence. [sent-19, score-0.485]
12 In summary, this is yet another problem where much is lost by going down the standard route of null hypothesis testing. [sent-22, score-0.08]
13 Better, in my view, to start with the admission of variation in the effect and go from there. [sent-23, score-0.245]
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same-blog 1 1.0 1215 andrew gelman stats-2012-03-16-The “hot hand” and problems with hypothesis testing
Introduction: Gur Yaari writes : Anyone who has ever watched a sports competition is familiar with expressions like “on fire”, “in the zone”, “on a roll”, “momentum” and so on. But what do these expressions really mean? In 1985 when Thomas Gilovich, Robert Vallone and Amos Tversky studied this phenomenon for the first time, they defined it as: “. . . these phrases express a belief that the performance of a player during a particular period is significantly better than expected on the basis of the player’s overall record”. Their conclusion was that what people tend to perceive as a “hot hand” is essentially a cognitive illusion caused by a misperception of random sequences. Until recently there was little, if any, evidence to rule out their conclusion. Increased computing power and new data availability from various sports now provide surprising evidence of this phenomenon, thus reigniting the debate. Yaari goes on to some studies that have found time dependence in basketball, baseball, voll
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Introduction: Phil pointed me to this paper so I thought I probably better repeat what I wrote a couple years ago: 1. The effects are certainly not zero. We are not machines, and anything that can affect our expectations (for example, our success in previous tries) should affect our performance. 2. The effects I’ve seen are small, on the order of 2 percentage points (for example, the probability of a success in some sports task might be 45% if you’re “hot” and 43% otherwise). 3. There’s a huge amount of variation, not just between but also among players. Sometimes if you succeed you will stay relaxed and focused, other times you can succeed and get overconfidence. 4. Whatever the latest results on particular sports, I can’t see anyone overturning the basic finding of Gilovich, Vallone, and Tversky that players and spectators alike will perceive the hot hand even when it does not exist and dramatically overestimate the magnitude and consistency of any hot-hand phenomenon that does exist.
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Introduction: Karl Broman writes : I [Karl] personally would avoid sports entirely, as I view the subject to be insufficiently serious. . . . Certainly lots of statisticians are interested in sports. . . . And I’m not completely uninterested in sports: I like to watch football, particularly Nebraska, Green Bay, and Baltimore, and to see Notre Dame or any team from Florida or Texas lose. But statistics about sports? Yawn. As a person who loves sports, statistics, and sports statistics, I have a few thoughts: 1. Not everyone likes sports, and even fewer are interested in any particular sport. It’s ok to use sports examples, but don’t delude yourself into thinking that everyone in the class cares about it. 2. Don’t forget foreign students. A lot of them don’t even know the rules of kickball, fer chrissake! 3. Of the students who care about a sport, there will be a minority who really care. We had some serious basketball fans in our class last year. 4. I think the best solution
Introduction: Hey, we all know the answer: “correlation does not imply causation”—but of course life is more complicated than that. As philosophers, economists, statisticians, and others have repeatedly noted, most of our information about the world is observational not experimental, yet we manage to draw causal conclusions all the time. Sure, some of these conclusions are wrong (more often than 5% of the time, I’m sure) but that’s an accepted part of life. Challenges in this regard arise in the design of a study, in the statistical analysis, in how you write it up for a peer-reviewed journal, and finally in how you present it to the world. School sports and life outcomes An interesting case of all this came up recently in a post on Freakonomics that pointed to a post on Deadspin that pointed to a research article . The claim was that “sports participation [in high school] causes women to be less likely to be religious . . . more likely to have children . . . more likely to be singl
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Introduction: Gur Yaari writes : Anyone who has ever watched a sports competition is familiar with expressions like “on fire”, “in the zone”, “on a roll”, “momentum” and so on. But what do these expressions really mean? In 1985 when Thomas Gilovich, Robert Vallone and Amos Tversky studied this phenomenon for the first time, they defined it as: “. . . these phrases express a belief that the performance of a player during a particular period is significantly better than expected on the basis of the player’s overall record”. Their conclusion was that what people tend to perceive as a “hot hand” is essentially a cognitive illusion caused by a misperception of random sequences. Until recently there was little, if any, evidence to rule out their conclusion. Increased computing power and new data availability from various sports now provide surprising evidence of this phenomenon, thus reigniting the debate. Yaari goes on to some studies that have found time dependence in basketball, baseball, voll
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Introduction: Phil pointed me to this paper so I thought I probably better repeat what I wrote a couple years ago: 1. The effects are certainly not zero. We are not machines, and anything that can affect our expectations (for example, our success in previous tries) should affect our performance. 2. The effects I’ve seen are small, on the order of 2 percentage points (for example, the probability of a success in some sports task might be 45% if you’re “hot” and 43% otherwise). 3. There’s a huge amount of variation, not just between but also among players. Sometimes if you succeed you will stay relaxed and focused, other times you can succeed and get overconfidence. 4. Whatever the latest results on particular sports, I can’t see anyone overturning the basic finding of Gilovich, Vallone, and Tversky that players and spectators alike will perceive the hot hand even when it does not exist and dramatically overestimate the magnitude and consistency of any hot-hand phenomenon that does exist.
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Introduction: Phil pointed me to this paper so I thought I probably better repeat what I wrote a couple years ago: 1. The effects are certainly not zero. We are not machines, and anything that can affect our expectations (for example, our success in previous tries) should affect our performance. 2. The effects I’ve seen are small, on the order of 2 percentage points (for example, the probability of a success in some sports task might be 45% if you’re “hot” and 43% otherwise). 3. There’s a huge amount of variation, not just between but also among players. Sometimes if you succeed you will stay relaxed and focused, other times you can succeed and get overconfidence. 4. Whatever the latest results on particular sports, I can’t see anyone overturning the basic finding of Gilovich, Vallone, and Tversky that players and spectators alike will perceive the hot hand even when it does not exist and dramatically overestimate the magnitude and consistency of any hot-hand phenomenon that does exist.
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