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andrew_gelman_stats 2011 knowledge graph

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1 andrew gelman stats-2011-12-31-Using factor analysis or principal components analysis or measurement-error models for biological measurements in archaeology?

Introduction: Greg Campbell writes: I am a Canadian archaeologist (BSc in Chemistry) researching the past human use of European Atlantic shellfish. After two decades of practice I am finally getting a MA in archaeology at Reading. I am seeing if the habitat or size of harvested mussels (Mytilus edulis) can be reconstructed from measurements of the umbo (the pointy end, and the only bit that survives well in archaeological deposits) using log-transformed measurements (or allometry; relationships between dimensions are more likely exponential than linear). Of course multivariate regressions in most statistics packages (Minitab, SPSS, SAS) assume you are trying to predict one variable from all the others (a Model I regression), and use ordinary least squares to fit the regression line. For organismal dimensions this makes little sense, since all the dimensions are (at least in theory) free to change their mutual proportions during growth. So there is no predictor and predicted, mutual variation of

2 andrew gelman stats-2011-12-30-Strings Attached: Untangling the Ethics of Incentives

Introduction: Chris Paulse points me to this book by Ruth Grant: Incentives can be found everywhere–in schools, businesses, factories, and government–influencing people’s choices about almost everything, from financial decisions and tobacco use to exercise and child rearing. So long as people have a choice, incentives seem innocuous. But Strings Attached demonstrates that when incentives are viewed as a kind of power rather than as a form of exchange, many ethical questions arise: How do incentives affect character and institutional culture? Can incentives be manipulative or exploitative, even if people are free to refuse them? What are the responsibilities of the powerful in using incentives? Ruth Grant shows that, like all other forms of power, incentives can be subject to abuse, and she identifies their legitimate and illegitimate uses. Grant offers a history of the growth of incentives in early twentieth-century America, identifies standards for judging incentives, and examines incentives

3 andrew gelman stats-2011-12-29-More by Berger and me on weakly informative priors

Introduction: A couple days ago we discussed some remarks by Tony O’Hagan and Jim Berger on weakly informative priors. Jim followed up on Deborah Mayo’s blog with this: Objective Bayesian priors are often improper (i.e., have infinite total mass), but this is not a problem when they are developed correctly. But not every improper prior is satisfactory. For instance, the constant prior is known to be unsatisfactory in many situations. The ‘solution’ pseudo-Bayesians often use is to choose a constant prior over a large but bounded set (a ‘weakly informative’ prior), saying it is now proper and so all is well. This is not true; if the constant prior on the whole parameter space is bad, so will be the constant prior over the bounded set. The problem is, in part, that some people confuse proper priors with subjective priors and, having learned that true subjective priors are fine, incorrectly presume that weakly informative proper priors are fine. I have a few reactions to this: 1. I agree

4 andrew gelman stats-2011-12-29-Bayes in astronomy

Introduction: David Schminovich points me to this paper by Yu Lu, H. Mo, Martin Weinberg, and Neal Katz: We believe that a wide range of physical processes conspire to shape the observed galaxy population but we remain unsure of their detailed interactions. The semi-analytic model (SAM) of galaxy formation uses multi-dimensional parameterisations of the physical processes of galaxy formation and provides a tool to constrain these underlying physical interactions. Because of the high dimensionality, the parametric problem of galaxy formation may be profitably tackled with a Bayesian-inference based approach, which allows one to constrain theory with data in a statistically rigorous way. In this paper we develop a SAM in the framework of Bayesian inference. . . . And here’s another from the same authors, this time on “Bayesian inference of galaxy formation from the K-band luminosity function of galaxies: tensions between theory and observation.” I haven’t actually looked at the papers but

5 andrew gelman stats-2011-12-28-“. . . extending for dozens of pages”

Introduction: Kaiser writes : I have read a fair share of bore-them-to-tears compilation of survey research results – you know, those presentations with one multi-colored, stacked or grouped bar chart after another, extending for dozens of pages. I hate those grouped bar charts also—as I’ve written repeatedly, the central role of almost all statistical displays is to make comparisons, and you can make twice as many comparisons with a line plot as a bar plot. But I suspect the real problem with the reports that Kaiser is talking about is the “extending for dozens of pages” part. If they could just print each individual plot smaller and put dozens on a page, you could maybe get through the whole report in two or three pages. Almost always, graphs are too large. I’ve even seen abominations such as a fifty-page report with a single huge pie chart on each page. As Kaiser says, think about communication! A report with one big pie chart or bar plot per page is like a text document with one w

6 andrew gelman stats-2011-12-28-Path sampling for models of varying dimension

Introduction: Somebody asks: Iâ€™m reading your paper on path sampling. It essentially solves the problem of computing the ratio \int q0(omega)d omega/\int q1(omega) d omega. I.e the arguments in q0() and q1() are the same. But this assumption is not always true in Bayesian model selection using Bayes factor. In general (for BF), we have this problem, t1 and t2 may have no relation at all. \int f1(y|t1)p1(t1) d t1 / \int f2(y|t2)p2(t2) d t2 As an example, suppose that we want to compare two sets of normally distributed data with known variance whether they have the same mean (H0) or they are not necessarily have the same mean (H1). Then the dummy variable should be mu in H0 (which is the common mean of both set of samples), and should be (mu1, mu2) (which are the means for each set of samples). One straight method to address my problem is to preform path integration for the numerate and the denominator, as both the numerate and the denominator are integrals. Each integral can be rewrit

7 andrew gelman stats-2011-12-28-Argument in favor of Ddulites

Introduction: Mark Palko defines a Ddulite as follows: A preference for higher tech solutions even in cases where lower tech alternatives have greater and more appropriate functionality; a person of ddulite tendencies. Though Ddulites are the opposite of Luddites with respect to attitudes toward technology, they occupy more or less the same point with respect to functionality. As a sometime Luddite myself (no cell phone, tv, microwave oven, etc.), I should in fairness point out the logic in favor of being a Ddulite. Old technology is typically pretty stable; new technology is improving. It can make sense to switch early (before the new technology actually performs better than the old) to get the benefits of being familiar with the new technology once it does take off.

8 andrew gelman stats-2011-12-27-“Keeping things unridiculous”: Berger, O’Hagan, and me on weakly informative priors

Introduction: Deborah Mayo sent me this quote from Jim Berger: Too often I see people pretending to be subjectivists, and then using “weakly informative” priors that the objective Bayesian community knows are terrible and will give ridiculous answers; subjectivism is then being used as a shield to hide ignorance. . . . In my own more provocative moments, I claim that the only true subjectivists are the objective Bayesians, because they refuse to use subjectivism as a shield against criticism of sloppy pseudo-Bayesian practice. This caught my attention because I’ve become more and more convinced that weakly informative priors are the right way to go in many different situations. I don’t think Berger was talking about me , though, as the above quote came from a publication in 2006, at which time I’d only started writing about weakly informative priors. Going back to Berger’s article , I see that his “weakly informative priors” remark was aimed at this article by Anthony O’Hagan, who w

9 andrew gelman stats-2011-12-27-The most dangerous jobs in America

Introduction: Robin Hanson writes: On the criteria of potential to help people avoid death, this would seem to be among the most important news I’ve ever heard. [In his recent Ph.D. thesis , Ken Lee finds that] death rates depend on job details more than on race, gender, marriage status, rural vs. urban, education, and income combined ! Now for the details. The US Department of Labor has described each of 807 occupations with over 200 detailed features on how jobs are done, skills required, etc.. Lee looked at seven domains of such features, each containing 16 to 57 features, and for each domain Lee did a factor analysis of those features to find the top 2-4 factors. This gave Lee a total of 22 domain factors. Lee also found four overall factors to describe his total set of 225 job and 9 demographic features. (These four factors explain 32%, 15%, 7%, and 4% of total variance.) Lee then tried to use these 26 job factors, along with his other standard predictors (age, race, gender, m

10 andrew gelman stats-2011-12-27-Laws as expressive

Introduction: June Carbone points out sometimes people want laws to express a sentiment. This isn’t just about Congress passing National Smoked Meats Week or San Francisco establishing itself as a nuclear-free zone, it also includes things such as laws against gay marriage, where, as Carbone writes, “we ‘care too much,’ when in fact we can do so little.” I don’t have anything to add here, and I expect many of you are familiar with this idea, but it’s new to me. I’d always been puzzled by people who want to use the law to express a sentiment, but perhaps it makes sense to be open-minded and to consider this as one of the purposes of the legislative process.

11 andrew gelman stats-2011-12-26-Tweeting the Hits?

Introduction: Someone sent me an email saying that he liked my little essay, “Descriptive statistics aren’t just for losers.” I had no idea what he was talking about, but it sounded like the kind of thing I’d say, so I searched the blog and found this post , which indeed I really like! I thanked my correspondent for reminding me of this little article I’d forgotten, and he told me he just learned of it via someone’s tweet. This made me think: Maybe I should have a twitter feed of nothing but old blog entries. I could just go back to 2004 and then go gradually forward, tweeting the items that I judge to remain of interest. Does this make sense? Or is there a better way to do this? ALternatively, I could do it as a separate blog, but that seems a bit . . . recursive.

12 andrew gelman stats-2011-12-26-The quals and the quants

Introduction: After I recently criticized Gregg Easterbrook for assigning Obama an implausible 90+% chance of beating Mitt Romney, some commenters thought I was being too critical, that I should cut Easterbrook some slack because he just was speaking metaphorically. In other words, Easterbrook is a “qual.” He uses numbers in his writing because that’s what everyone is supposed to do nowadays, but he doesn’t intend those numbers to be meant literally. Similarly, he presumably didn’t really mean it when he wrote that Scott Brown and Elizabeth Warren “couldn’t be more different — personally or politically.” And he had no problem typing that Obama’s approval rating was 23% because, to him, “23%” is just another word for “low.” He’s a qual, that’s all. Similarly, when Samantha Power was just being a qual when she wrote the meaningful-sounding but actually empty statement, “Since 1968, with the single exception of the election of George W. Bush in 2000, Americans have chosen Republican pres

13 andrew gelman stats-2011-12-25-Further evidence of a longstanding principle of statistics

Introduction: The principle is, Whatever you do, somebody in psychometrics already did it long before. The new evidence comes from an article by Lawrence Hubert and Howard Wainer: There are several issues with the use of ecological correlations: They tend to be a lot higher than individual-level correlations, and assuming what is seen at the group level also holds at the level of the individual is so pernicious, it has been labeled the “ecological fallacy” by Selvin (1958). The term ecological correlation was popularized from a 1950 article by William Robinson (Robinson, 1950), but the idea has been around for some time (e.g., see the 1939 article by E. L. Thorndike, On the Fallacy of Imputing Correlations Found for Groups to the Individuals or Smaller Groups Composing Them).

14 andrew gelman stats-2011-12-24-Statistical ethics violation

Introduction: A colleague writes: When I was in NYC I went to this party by group of Japanese bio-scientists. There, one guy told me about how the biggest pharmaceutical company in Japan did their statistics. They ran 100 different tests and reported the most significant one. (This was in 2006 and he said they stopped doing this few years back so they were doing this until pretty recently…) I’m not sure if this was 100 multiple comparison or 100 different kinds of test but I’m sure they wouldn’t want to disclose their data… Ouch!

15 andrew gelman stats-2011-12-24-Latest in blog advertising

Introduction: I received the following message from “Patricia Lopez” of “Premium Link Ads”: Hello, I am interested in placing a text link on your page: http://andrewgelman.com/2011/07/super_sam_fuld/. The link would point to a page on a website that is relevant to your page and may be useful to your site visitors. We would be happy to compensate you for your time if it is something we are able to work out. The best way to reach me is through a direct response to this email. This will help me get back to you about the right link request. Please let me know if you are interested, and if not thanks for your time. Thanks. Usually I just ignore these, but after our recent discussion I decided to reply. I wrote: How much do you pay? But no answer. I wonder what’s going on? I mean, why bother sending the email in the first place if you’re not going to follow up?

16 andrew gelman stats-2011-12-23-Surveys show Americans are populist class warriors, except when they aren’t

Introduction: From my New York Times blog today, here’s an example of how contemporaneous poll results can be given exactly opposite interpretations. Recently in the New Republic, William Galston shared some recent findings from Gallup: Respondents were asked to categorize three economic objectives as extremely important, very important, somewhat important, or not important. Here’s what they said: Extremely/very important Somewhat/not important Grow and expand the economy 82 18 Increase equality of opportunity for people to get ahead 70 30 Reduce the income and wealth gap between the rich and the poor 46 54 When Gallup asked a sample of Americans in 1998 whether the gap between the rich and the poor was a problem that needed t

17 andrew gelman stats-2011-12-22-Tables as graphs: The Ramanujan principle

Introduction: Tables are commonly read as crude graphs: what you notice in a table of numbers is (a) the minus signs, and thus which values are positive and which are negative, and (b) the length of each number, that is, its order of magnitude. The most famous example of such a read might be when the mathematician Srinivasa Ramanujan supposedly conjectured the asymptotic form of the partition function based on a look at a table of the first several partition numbers: he was essentially looking at a graph on the logarithmic scale. I discuss some modern-day statistical examples in this article for Significance magazine . I had a lot of fun creating the “calculator font” for the above graph in R and then writing the article. I hope you enjoy it too! P.S. Also check out this short note by Marcin Kozak and Wojtek Krzanowski on effective presentation of data. P.P.S. I wrote this blog entry a month ago and had it in storage. Then my issue of Significance came in the mail—with my

18 andrew gelman stats-2011-12-21-In which I compare “POLITICO’s chief political columnist” unfavorably to a cranky old dead guy and one of the funniest writers who’s ever lived

Introduction: Neil Malhotra writes: I just wanted to alert to this completely misinformed Politico article by Roger Simon, equating sampling theory with “magic.” Normally, I wouldn’t send you this, but I sent him a helpful email and he was a complete jerk about it. Wow—this is really bad. It’s so bad I refuse to link to it. I don’t know who this dude is, but it’s pitiful. Andy Rooney could do better. And I don’t mean Andy Rooney in his prime, I mean Andy Rooney right now. The piece appears to be an attempt at jocularity, but it’s about 10 million times worse than whatever the worst thing is that Dave Barry has ever written. My question to Neil Malhotra is . . . what made you click on this in the first place? P.S. John Sides piles on with some Gallup quotes.

19 andrew gelman stats-2011-12-21-Derman, Rodrik and the nature of statistical models

Introduction: Interesting thoughts from Kaiser Fung. Derman seems to have a point in his criticisms of economic models—and things are just as bad in other social sciences. (I’ve criticized economists and political scientists for taking a crude, 80-year-old model of psychology as “foundational,” but even more sophisticated models in psychology and sociology have a lot of holes, if you go outside of certain clearly bounded areas such as psychometrics.) What can be done, then? One approach, which appeals to me as a statistician, is to more carefully define one’s range of inquiry. Even if we don’t have a great model of political bargaining, we can still use ideal-point models to capture a lot of the variation in legislative voting. And, in my blog post linked to above, I recommended that economists forget about coming up with the grand unified theory of human behavior (pretty impossible, given that they still don’t want to let go of much of their folk-psychology models) and put more effort i

20 andrew gelman stats-2011-12-20-This guy has a regular column at Reuters

Introduction: Gregg Easterbrook : Gingrich is a wild card. He probably would end up a flaming wreckage in electoral terms, but there’s a chance he could become seen as the man unafraid to bring sweeping change to an ossified Washington, D.C. There’s perhaps a 90 percent likelihood Obama would wipe the floor with Gingrich, versus a 10 percent likelihood Gingrich would stage an historic upset. This is the dumbest thing I’ve seen since . . . ummm, I dunno, how bout this ? It actually gets worse because Easterbrook then invokes game theory. What next? Catastrophe theory? Intelligent design? P.S. Maybe I should explain for readers without an education in probability theory. Let’s suppose “wipe the floor” means that Obama gets 55%+ of the two-party vote, and let’s suppose that “an historic upset” means that Obama gets less than 50% of the vote. Now try to draw a forecast distribution that has 90% of its probability above 0.55 and 10% of it’s probability below 0.50. It’s a pretty weird-loo