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David Christopher Bell goes to the trouble (link from Palko) to explain why “Every Map of ‘The Most Popular _________ by State’ Is Bullshit.”

As long as enterprising P.R. firms are willing to supply unsourced data, lazy journalists (or whatever you call these people) will promote it.

We saw this a few years ago in a Wall Street Journal article by Robert Frank (not the academic economist of same name) that purported to give news on the political attitudes of the super-rich but really was actually just credulously giving reporting unsubstantiated statements from some consulting company.

And of course we saw this a couple years ago when New York Times columnist David Brooks promoted some fake statistics on ethnicity and high school achievement.

I get it: journalism is hard work, and sometimes a reporter or columnist will take a little break and just report a press release or promote the claims of some political ideologue. It happens. But I don’t have to like it.

What’s the worst joke you’ve ever heard?

When I say worst, I mean worst. A joke with no redeeming qualities.

Here’s my contender, from the book “1000 Knock-Knock Jokes for Kids”:

– Knock Knock.
– Who’s there?
– Ann
– Ann who?
– An apple fell on my head.

There’s something beautiful about this one. It’s the clerihew of jokes. Zero cleverness. It lacks any sense of inevitability, in that any sentence whatsoever could work here, as long as it begins with the word “An.”

Stock, flow, and two smoking regressions


In a comment on our recent discussion of stock and flow, Tom Fiddaman writes:

Here’s an egregious example of statistical stock-flow confusion that got published.

Fiddaman is pointing to a post of his from 2011 discussing a paper that “examines the relationship between CO2 concentration and flooding in the US, and finds no significant impact.”

Here’s the title and abstract of the paper in question:

Has the magnitude of floods across the USA changed with global CO2 levels?

R. M. Hirsch & K. R. Ryberg


Statistical relationships between annual floods at 200 long-term (85–127 years of record) streamgauges in the coterminous United States and the global mean carbon dioxide concentration (GMCO2) record are explored. The streamgauge locations are limited to those with little or no regulation or urban development. The coterminous US is divided into four large regions and stationary bootstrapping is used to evaluate if the patterns of these statistical associations are significantly different from what would be expected under the null hypothesis that flood magnitudes are independent of GMCO2. In none of the four regions defined in this study is there strong statistical evidence for flood magnitudes increasing with increasing GMCO2. One region, the southwest, showed a statistically significant negative relationship between GMCO2 and flood magnitudes. The statistical methods applied compensate both for the inter-site correlation of flood magnitudes and the shorter-term (up to a few decades) serial correlation of floods.

And here’s Fiddaman’s takedown:

There are several serious problems here.

First, it ignores bathtub dynamics. The authors describe causality from CO2 -> energy balance -> temperature & precipitation -> flooding. But they regress:

ln(peak streamflow) = beta0 + beta1 × global mean CO2 + error

That alone is a fatal gaffe, because temperature and precipitation depend on the integration of the global energy balance. Integration renders simple pattern matching of cause and effect invalid. For example, if A influences B, with B as the integral of A, and A grows linearly with time, B will grow quadratically with time.

This sort of thing comes up a lot in political science, where the right thing to do is not so clear. For example, suppose we’re comparing economic outcomes under Democratic and Republican presidents. The standard thing to look at is economic growth. But maybe it is changes in growth that should matter? As Jim Campbell points out, if you run a regression using economic growth as an outcome, you’re implicitly assuming that these effects on growth persist indefinitely, and that’s a strong assumption.

Anyway, back to Fiddaman’s critique of that climate-change regression:

The situation is actually worse than that for climate, because the system is not first order; you need at least a second-order model to do a decent job of approximating the global dynamics, and much higher order models to even think about simulating regional effects. At the very least, the authors might have explored the usual approach of taking first differences to undo the integration, though it seems likely that the data are too noisy for this to reveal much.

Second, it ignores a lot of other influences. The global energy balance, temperature and precipitation are influenced by a lot of natural and anthropogenic forcings in addition to CO2. Aerosols are particularly problematic since they offset the warming effect of CO2 and influence cloud formation directly. Since data for total GHG loads (CO2eq), total forcing and temperature, which are more proximate in the causal chain to precipitation, are readily available, using CO2 alone seems like willful ignorance. The authors also discuss issues “downstream” in the causal chain, with difficult-to-assess changes due to human disturbance of watersheds; while these seem plausible (not my area), they are not a good argument for the use of CO2. The authors also test other factors by including oscillatory climate indices, the AMO, PDO and ENSO, but these don’t address the problem either. . . .

I’ll skip a bit, but there’s one more point I wanted to pick up on:

Fourth, the treatment of nonlinearity and distributions is a bit fishy. The relationship between CO2 and forcing is logarithmic, which is captured in the regression equation, but I’m surprised that there aren’t other important nonlinearities or nonnormalities. Isn’t flooding heavy-tailed, for example? I’d like to see just a bit more physics in the model to handle such issues.

If there’s a monotonic pattern, it should show up even if the functional form is wrong. But in this case Fiddaman has a point, in that the paper he’s criticizing makes a big deal about not finding a pattern, in which case, yes, using a less efficient model could be a problem.

Similarly with this point:

Fifth, I question the approach of estimating each watershed individually, then examining the distribution of results. The signal to noise ratio on any individual watershed is probably pretty horrible, so one ought to be able to do a lot better with some spatial pooling of the betas (which would also help with issue three above).

Fiddaman concludes:

I think that it’s actually interesting to hold your nose and use linear regression as a simple screening tool, in spite of violated assumptions. If a relationship is strong, you may still find it. If you don’t find it, that may not tell you much, other than that you need better methods. The authors seem to hold to this philosophy in the conclusion, though it doesn’t come across that way in the abstract.

An inundation of significance tests

Jan Vanhove writes:

The last three research papers I’ve read contained 51, 49 and 70 significance tests (counting conservatively), and to the extent that I’m able to see the forest for the trees, mostly poorly motivated ones.

I wonder what the motivation behind this deluge of tests is.
Is it wanton obfuscation (seems unlikely), a legalistic conception of what research papers are (i.e. ‘don’t blame us, we’ve run that test, too!’) or something else?

Perhaps you know of some interesting paper that discusses this phenomenon? Or whether it has an established name?
It’s not primarily the multiple comparisons problem but more the inundation aspect I’m interested in here.

He also links to this post of his on the topic. Just a quick comment on his post: he is trying to estimate a treatment effect via a before-after comparison, he’s plotting y-x vs. x and running into a big regression-to-the-mean pattern:

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Actually he’s plotting y/x not y-x but that’s irrelevant for the present discussion.

Anyway, I think he should have a treatment and a control group and plot y vs. x (or, in this case, log y vs. log x) with separate lines for the two groups: the difference between the lines represents the treatment effect.

I don’t have an example with his data but here’s the general idea:

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Back to the original question: I think it’s good to display more rather than less but I agree with Vanhove that if you want to display more, just display raw data. Or, if you want to show a bunch of comparisons, please structure them in a reasonable way and display as a readable grid. All these p-values in the text, they’re just a mess.

Thinking about this from a historical perspective, I feel (or, at least, hope) that null hypothesis significance tests—whether expresses using p-values, Bayes factors, or any other approach—are on their way out. But, until they go away, we may be seeing more and more of them leading to the final flame-out.

In the immortal words of Jim Thompson, it’s always lightest just before the dark.

On deck this week

Mon: An inundation of significance tests

Tues: Stock, flow, and two smoking regressions

Wed: What’s the worst joke you’ve ever heard?

Thurs: > Huffington Post, Wall Street Journal, New York Times

Fri: Measurement is part of design

Sat: “17 Baby Names You Didn’t Know Were Totally Made Up”

Sun: What to do to train to apply statistical models to political science and public policy issues

Chess + statistics + plagiarism, again!


In response to this post (in which I noted that the Elo chess rating system is a static model which, paradoxically, is used to for the purposes of studying changes), Keith Knight writes:

It’s notable that Glickman’s work is related to some research by Harry Joe at UBC, which in turn was inspired by data provided by Nathan Divinsky who was (wait for it) a co-author of one of your favourite plagiarists, Raymond Keene.

In the 1980s, Keene and Divinsky wrote a book, Warriors of the Mind, which included an all-time ranking of the greatest chess players – it was actually Harry Joe who did the modeling and analysis although Keene and Divinsky didn’t really give him credit for it. (Divinsky was a very colourful character – he owned a very popular restaurant in Vancouver and was briefly married to future Canadian Prime Minister Kim Campbell. Certainly not your typical Math professor!)

I wonder what Chrissy would think of this?

Knight continues:

And speaking of plagiarism, check out the two attached papers. Somewhat amusingly (and to their credit), the plagiarized version actually cites the original paper!

Screen Shot 2015-03-24 at 10.28.20 PM

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“Double Blind,” indeed!

Kaiser’s beef


The Numbersense guy writes in:

Have you seen this?

It has one of your pet peeves… let’s draw some data-driven line in the categorical variable and show significance.

To make it worse, he adds a final paragraph saying essentially this is just a silly exercise that I hastily put together and don’t take it seriously!

Kaiser was pointing me to a news article by economist Justin Wolfers, entitled “Fewer Women Run Big Companies Than Men Named John.”

Here’s what I wrote back to Kaiser:

I took a look and it doesn’t seem so bad. Basically the sex difference is so huge that it can be dramatized in this clever way. So I’m not quite sure what you dislike about it.

Kaiser explained:

Here’s my beef with it…

Just to make up some numbers. Let’s say there are 500 male CEOs and 25 female CEOs so the aggregate index is 20.

Instead of reporting that number, they reduce the count of male CEOs while keeping the females fixed. So let’s say 200 of those male CEOs are named Richard, William, John, and whatever the 4th name is. So they now report an index of 200/25 = 8.

Problem 1 is that this only “works” if they cherry pick the top male names, probably the 4 most common names from the period where most CEOs are born. As he admitted at the end, this index is not robust as names change in popularity over time. Kind of like that economist who said that anyone whose surname begins with A-N has a better chance of winning the Nobel Prize (or some such thing).

Problem 2: we may need an experiment to discover which of the following two statements are more effective/persuasive:

a) there are 20 male CEOs for every female CEO in America
b) there are 8 male CEOs named Richard, Wiliam, John and David for every female CEO in America

For me, I think b) is more complex to understand and in fact the magnitude of the issue has been artificially reduced by restricting to 4 names!

How about that?

I replied that I agree that the picking-names approach destroys much of the quantitative comparisons. Still, I think the point here is that the differences are so huge that this doesn’t matter. It’s a dramatic comparison. The relevant point, perhaps, is that these ratios shouldn’t be used as any sort of “index” for comparisons between scenarios. If Wolfers just wants to present the story as a way of dramatizing the underrepresentation of women, that works. But it would not be correct to use this to compare representation of women in different fields or in different eras.

I wonder if the problem is that econ has these gimmicky measures, for example the cost-of-living index constructed using the price of the Big Mac, etc. I don’t know why, but these sorts of gimmicks seem to have some sort of appeal.

John Lott as possible template for future career of “Bruno” Lacour

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The recent story about the retracted paper on political persuasion reminded me of the last time that a politically loaded survey was discredited because the researcher couldn’t come up with the data.

I’m referring to John Lott, the “economist, political commentator, and gun rights advocate” (in the words of Wikipedia) who is perhaps more well known on the internet by the name of Mary Rosh, an alter ego he created to respond to negative comments (among other things, Lott used the Rosh handle to refer to himself as “the best professor I ever had”).

Again from Wikipedia:

Lott claimed to have undertaken a national survey of 2,424 respondents in 1997, the results of which were the source for claims he had made beginning in 1997. However, in 2000 Lott was unable to produce the data, or any records showing that the survey had been undertaken. He said the 1997 hard drive crash that had affected several projects with co-authors had destroyed his survey data set, the original tally sheets had been abandoned with other personal property in his move from Chicago to Yale, and he could not recall the names of any of the students who he said had worked on it. . . .

On the other hand, Rosh Lott has continued to insist that the survey actually happened. So he shares that with Michael LaCour, the coauthor of the recently retracted political science paper.

I have nothing particularly new to say about either case, but I was thinking that some enterprising reporter might call up Lott and see what he thinks about all this.

Also, Lott’s career offers some clues as to what might happen next to LaCour. Lott’s academic career dissipated and now he seems to spend his time running an organization called the Crime Prevention Research Center which is staffed by conservative scholars, so I guess he pays the bills by raising funds for this group.

One could imagine LaCour doing something similar—but he got caught with data problems before receiving his UCLA social science PhD, so his academic credentials aren’t so strong. But, speaking more generally, given that it appears that respected scholars (and, I suppose, funders, but I can’t be so sure of that as I don’t see a list of funders on the website) are willing to work with Lott, despite the credibility questions surrounding his research, I suppose that the same could occur with LaCour. Perhaps, like Lott, he has the right mixture of ability, brazenness, and political commitment to have a successful career in advocacy.

The above might all seem like unseemly speculation—and maybe it is—but this sort of thing is important. Social science isn’t just about the research (or, in this case, the false claims masquerading as research); it’s also about the social and political networks that promote the work.

Creativity is the ability to see relationships where none exist

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Brent Goldfarb and Andrew King, in a paper to appear in the journal Strategic Management, write:

In a recent issue of this journal, Bettis (2012) reports a conversation with a graduate student who forthrightly announced that he had been trained by faculty to “search for asterisks”. The student explained that he sifted through large databases for statistically significant results and “[w]hen such models were found, he helped his mentors propose theories and hypotheses on the basis of which the ‘asterisks’ might be explained” (p. 109). Such an approach, Bettis notes, is an excellent way to find seemingly meaningful patterns in random data. He expresses concern that these practices are common, but notes that unfortunately “we simply do not have any baseline data on how big or small are the problems” (Bettis, 2012: p. 112).

In this article, we [Goldfarb and King] address the need for empirical evidence . . . in research on strategic management. . . .

Bettis (2012) reports that computer power now allows researchers to sift repeatedly through data in search of patterns. Such specification searches can greatly increase the probability of finding an apparently meaningful relationship in random data. . . . just by trying four functional forms for X, a researcher can increase the chance of a false positive from one in twenty to about one in six. . . .

Simmons et. al (2011) contend that some authors also push almost significant results over thresholds by removing or gathering more data, by dropping experimental conditions, by adding covariates to specified models, and so on.

And, beyond this, there’s the garden of forking paths: even if a researcher performs only one analysis of a given dataset, the multiplicity of choices involved in data coding and analysis are such that we can typically assume that different comparisons would have been studied had the data been different. That is, you can have misleading p-values without any cheating or “fishing” or “hacking” going on.

Goldfarb and King continue:

When evidence is uncertain, a single example is often considered representative of the whole (Tversky & Kahneman, 1973). Such inference is incorrect, however, if selection occurs on significant results. In fact, if “significant” results are more likely to be published, coefficient estimates will inflate the true magnitude of the studied effect — particularly if a low powered test has been used (Stanley, 2005).

They conducted a study of “estimates reported in 300 published articles in a random stratified sample from five top outlets for research on strategic management . . . [and] 60 additional proposals submitted to three prestigious strategy conferences.”

And here’s what they find:

We estimate that between 24% and 40% of published findings based on “statistically significant” (i.e. p<0.05) coefficients could not be distinguished from the Null if the tests were repeated once. Our best guess is that for about 70% of non-confirmed results, the coefficient should be interpreted to be zero. For the remaining 30%, the true B is not zero, but insufficient test power prevents an immediate replication of a significant finding. We also calculate that the magnitude of coefficient estimates of most true effects are inflated by 13%.

I’m surprised their estimated exaggeration factor is only 13%; I’d have expected much higher, even if only conditioning on “true” effects (however that is defined).

I have not tried to follow the details of the authors’ data collection and analysis process and thus can neither criticize nor endorse their specific findings. But I’m sympathetic to their general goals and perspective.

As a commenter wrote in an earlier discussion, it is the combination of a strawman with the concept of “statistical significance” (ie the filtering step) that seems to be a problem, not the p-value per se.

Weggy update: it just gets sadder and sadder

Uh oh, lots on research misconduct lately. Newest news is that noted Wikipedia-lifter Ed Wegman sued John Mashey, one of his critics, for $2 million dollars. Then he backed down and decided not to sue after all.

Best quote from Mashey’s write-up:

None of this made any sense to me, but then I am no lawyer. As it turned out, it made no sense to good lawyers either . . .

Lifting an encyclopedia is pretty impressive and requires real muscles. Lifting from Wikipedia, not so much.

In all seriousness, this is really bad behavior. Copying and garbling material from other sources and not giving the references? Uncool. Refusing to admit error? That’ll get you a regular column in a national newspaper. A 2 million dollar lawsuit? That’s unconscionable escalation, it goes beyond chutzpah into destructive behavior. I don’t imagine that Raymond Keene Bernard Dunn would be happy about what is being done in his name.