I can't avoid all my problems by drawing squirrels, but when I can, I do.

--Randall Munrow

There's a sort of Gresham's Law of conversations. If a conversation reaches a certain level of incivility, the more thoughtful people start to leave.

--Paul Graham

but timing isn't one of them.

Hm? What Pisani is pointing out here is that of the 3 major causal patterns that a cross-sectional correlation can reflect, A->B, B->A and A<-C->B, a longitudinal correlation in which observations of A are followed by observations of B, will let you rule out 1 of the 3 patterns (B->A), reverse causation, which leaves either the hypothesized direct causation or confounding. This is much better evidence than just the cross-sectional approach, although I think confounding is much more likely in general so the boost is not as big as the trichotomy makes it sound.

I think the common thread in a lot of these [horrible] relationships is people who have managed to go through their entire lives without realizing that “Person did Thing, which caused me to be upset” is not the same thing as “Person did something wrong”, much less “I have a right to forbid Person from ever doing Thing again”.

--Ozymandias (most of the post is unrelated)

I think that the lifespan that humans can live to if they wish, given current medical and scientific knowledge, is too low.

I picked up the folders for the two courses required of every student at the school. Statistics and epidemiology. Epi—what?

In the first lecture, we ‘reviewed’ all the major study types. For example, in the case-control study you find a group of people with a disease, and then look for people who are much the same but without the disease. You compare the two groups to see if they have different risks. It’s a relatively cheap method, but it doesn’t tell you much about the order in which things happen. I can’t remember all the examples used in the lecture, but let’s say you want to look at causes of depression in women. You start with 600 depressed women, find another 600 who match them in age, ethnicity and educational status, and then ask them all about their lives. Let’s say you find out that women who are depressed are six times more likely not to have had sex in the last year as women who are cheerful. That means if you’re not having sex you get depressed, right? But hang on, couldn’t it be that women who are moping around looking miserable don’t get laid much?

Perhaps you’d be better off with a cohort study. You start off with several thousand women who are perfectly happy. Then you follow them over time, recording their behaviours, and see which of them get depressed. If you find that women who have sex are less likely to become depressed than women who aren’t getting any, it suggests it is the lack of sex that causes the depression, not the depression which stops you getting laid. You can throw out the ‘misery guts’ theory and recommend more good sex as an intervention to promote mental health.

-- Elizabeth Pisani, The Wisdom of Whores, p. 16

Don't trust any model that implies X is too low unless it's also capable of detecting when X would be too high

SilasX

The smug mask of virtue triumphant could be almost as horrible as the face of wickedness revealed. Almost as horrible, but not quite.

-- Granny Weatherwax. Carpe Jugulum, Terry Pratchett

[T]he kind of mirage that came from modern data-dredging capabilities: if you watch trillions of things, you will often see one-in-a-million coincidences.

-- Vernor Vinge, Rainbows End

What if everyone knows that all the models are flawed, but the geocentric model makes the best predictions in one sub-domain, and the heliocentric model in another?