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October 22, 2014


Sophia Grene

Not sure it's exactly what you're looking for, but here's my anecdote.
I have cycled as my main form of urban transport for many years. When I moved to London, I started wearing a helmet, but then did some reading around whether that was a sensible safety precaution. I came to the conclusion that I felt comfortable with not wearing a helmet, so now I cycle without.
So far, so good.
But one day a much respected colleague, also a cyclist, asked why I didn't wear a helmet (she does). I explained that my understanding of the research led me to believe that it wasn't a particularly useful thing to do. She was genuinely shocked that I was applying statistics to my real life, and clearly disapproved.
People don't like to make that link.

Luis Enrique

I don't understand the technicalities of how to adjust significance thresholds when you look at multiple models, but I am a bit wary of the idea data mining is bad econometrics.

Kieran Martin

Essentially you are generating replications. Importantly, given a hypothesis based on data mining, you have then explored it in lots of different circumsances, and found that the hypothesis seems to hold. That's a fairly scientific approach.

Having a solid theory to explain statistical data is useful as well, as correlations on their own could just be randomness, although one should obviously be wary of post hoc theories created to explain data.

Basically then: mine the data, knowing that you will almost certainly pick out trends which are statistical artifacts. Try to explain those trends with sensible theories. For those that make some kind of theoretical sense to you, see if you can replicate those results. If you can, then you have decent evidence that something is going on.

George H. Blackford

I don't think there are any statistics that would make me feel comfortable in encouraging my children not to ware a helmet while cycling in urban traffic. I sure would like to see the research that you read.


An underlying assumption is that the subject is a person able to change their mind, willing to change their beliefs to fit the data.
I've found very few people like this.

Peter Dorman

Replication is central, of course. Stats books (the ones I've seen) don't make a big point of this, so when I teach statistics I go out of my way to show how much more important it is than whatever p value you get in a single study. (Not to mention the specification mining that generates that p value.) Nevertheless, there's a big caveat: replication does its job to the extent that the different studies are truly independent of each other. First off is the difference in data sets, which is what moved you about momentum effects. Good. But another concern is that the results you see in any particular set are dependent on the assumptions packed into the data collection and analysis methods underlying them. If these assumptions are not mandatory or self-evident, there may be other ways of doing such a study. In that case the power of replication depends on whether you see the same results across a variety of methodological choices.

I mention this because I've encountered quite a bit of replication in economics that doesn't convince at all because the same dodgy methods are applied to every data set. (Exhibit A is the value of statistical life literature.)

Frank de Libero

Good writing, including statistical, requires a belief in symmetrical conversation between writer and reader, a mutual responsibility to further understanding. My sense is Chris' post assumes that, and that the persuasion is focused on the intelligent engaged reader, not just another economist. I think that should be explicit.

Given that, there's the rhetorical ideal of ethos, pathos, logos. I believe many symbolic analysts (e.g., economists, statisticians) go directly to logos. I used to do that, attempting to persuade solely by the use of reasoning, largely ignoring ethos and pathos, character and emotion. As I see it, ethos in analytical writing is more about conveying that you care; furthermore not just caring about the issues but also in the sense of diligence, about having been thorough. Narrative, such as a story or example, can be a useful way to convey a sense of pathos. If you want to persuade analytically and you're writing for the intelligent engaged reader, then ethos, pathos, logos—all three—should be part of the deal.

One other thought is that for the writing to be persuasive it should answer "Is it reasonable?" Reasonableness runs through Chris' examples and may also be reflected in Sophia's bicycle helmet example, though Sophia is the person to judge that.

Chris asked for examples, which I don't have off hand. Perhaps others do?

Note: A helpful and fun discussion of "ethos, pathos, logos" is here:


I would argue the emergence of neoliberalism and its acceptance wasn't due to diversity, but the opposite.

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