6 More Selection Effects

1) "How do you figure out if someone is vegan?" "Don't worry, they'll tell you."

This is a selection effect; if someone just quietly orders animal-less things whenever you eat out together, and otherwise keeps their diet to themselves, you might be friends for years without discovering their veganicity; people merely think vegans are always announcing it because the ones who announce it are the ones they're aware of. Ditto for Crossfitters, pilots and Harvardians.

2) "Well Behaved Women Seldom Make History" is a claim about a selection effect, not about the causal impact of different levels of rebelliousness.

Specifically, it comes from historian Laurel Thatcher Ulrich's paper "Vertuous Women Found," arguing that well behaved women mattered greatly in 17th Century New England, but had been neglected in modern (1970s) scholarship because they seemed "humdrum" compared to "antinomians and witches," so they Seldom Make [it into] History [books].

3) "You start thinking you're good, because the people who come to see you all like you," said the sage. "But, the reason they came to see you is because they like you."

4) The night before he was assassinated, Martin Luther King gave his famous Mountaintop speech. Incredibly you can watch a recording; it's one of the most harrowing things I've ever seen. He ends:

Like anybody, I would like to live a long life, longevity has its place. But I'm not concerned about that now. I just want to do God's will. And he has allowed me to go up to the mountain. And I've looked over, and I've seen the promised land. I may not get there with you. But I want you to know tonight, that we as a people will get to the promised land.

The first time I saw it I thought: this is unreal, it's like he knew he was going to die tomorrow. But the real story is equally harrowing, just in a different way: he'd spent ten years at this point surviving assassination attempts, and he spoke often about the possibility of his murder.

5) "I'm not saying you're self-censoring," says the critic to the journalist interviewing him. "I'm sure you believe everything you're saying. But what I'm saying is, if you believed something different, you wouldn't be sitting where you're sitting."

6) A thing that is said sometimes is that one night stands are never actually good in terms of the [redacted].

But that's obviously a selection effect: if you both enjoy the [redacted], you're far more likely to do it again in future, which retroactively makes it not-a-one-night-stand.

The correct analysis would have to be something like "first encounters between people who are not already dating, are, on average, not especially good," which may still be true, but it's important to get the sample right.

see previous: 9 Selection Effects