Crémieux Profile picture
Oct 4, 2024 • 10 tweets • 4 min read • Read on X
There are people who desperately want this to be untrue🧵

One example of this came up earlier this year, when a "Professor of Public Policy and Governance" accused other people of being ignorant about SAT scores because, he alleged, high schools predicted college grades better.Image
The thread in question was, ironically, full of irrelevant points that seemed intended to mislead, accompanied by very obvious statistical errors.

For example, one post in it received a Community Note for conditioning on a collider. Image
But let's ignore the obvious things. I want to focus on this one: the idea that high schools explain more of student achievement than SATs

The evidence for this? The increase in R^2 going from a model without to a model with high school fixed effects

This interpretation is bad. Image
The R^2 of the overall model did not increase because high schools are more important determinants of student achievement. This result cannot be interpreted to mean that your zip code is more important than your gumption and effort in school.

If we open the report, we see this:Image
Students from elite high schools and from disadvantaged ones receive similar results when it comes to SATs predicting achievement. If high schools really explained a lot, this wouldn't be the case.

What we're seeing is a case where R^2 was misinterpreted.
The reason the model R^2 blew up was because there's a fixed effect for every high school mentioned in this national-level dataset

That means that all the little differences between high schools are controlled—a lot of variation!—so the model is overfit, explaining the high R^2
This professor should've known better for many reasons.

For example, we know there's more variation between classrooms than between school districts when it comes to student achievement.

As another example, we know that achievement gaps exist along the whole continuum of school and district quality.

If the issue was really zip codes, high schools, and so on, this shouldn't be the case.

The other thing this professor should've known is that high school is biased! GPAs are biased too!

The bias in GPAs has actually been exploited: elite high schools inflate grades and don't report class ranks, so students appear better than they are. Image
But you know what isn't a biased tool for admissions? Just one thing: test scores.

Want to learn more? Here are some sources:

x.com/cremieuxrecuei…

cremieux.xyz/p/what-happens…

cremieux.xyz/p/bias-in-admi…

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More from @cremieuxrecueil

Apr 2
A new meta-analysis and systematic review on the effects of social media abstinence interventions on mental health has been published.

First result: No effect on positive affect: Image
Second result: No effect on negative affect. Image
Third result: No effect on life satisfaction in general. Image
Read 6 tweets
Apr 2
Happy Autism Awareness Day! I think too many people are 'aware' of autism.

Have you ever met someone who claims to be autistic, but they've never been diagnosed?

Self-reported autism spectrum disorder (ASD) is practically uncorrelated with real, clinician-diagnosed autism🧵 Image
Sort self-reporters into those with high and low ASD scores, and you get the bars on the left. The "high-trait" self-reporters look like people with diagnosed autism (ASD column).

But they're more socially anxious (middle) and avoidant (right). Image
So far, the means of distinguishing diagnosed from self-reported autistics have been crude.

To get a more nuanced understanding of their differences, we have to look at behavior.

For that, we'll start with the social control task.
Read 14 tweets
Apr 1
Ending Credentialism could mark the beginning of an era of American rebirth, with benefits for everyone🧵

For starters, it could mean young people get to enjoy more of their adult lives being adults: Image
Ending credentialism means affirmative action will become less harmful, and you can be more confident that your doctor is qualified rather than someone who replaced a qualified person in the pipeline. Image
Without credentialism, women's ability to select on educational credentials will be impaired, and they'll have to make better judgments.

Men aiming to leverage credentialism in the dating market in their favor will lose that edge, too. But that's good, because it's a lousy edge. Image
Read 9 tweets
Mar 31
I just updated one of my articles a second time.

It has to do with Justice Jackson's comments that when Black newborns are delivered by Black doctors, they're much more likely to survive, justifying racially discriminatory admissions.

We now know the study contained fraud🧵 Image
The original article claimed that, when Black babies are attended to by Black physicians, their infant mortality rates decline substantially relative to when they have a White physician.

Justice Jackson cited this in the Supreme Court, even though it was implausible. Image
A few months back, we learned that the original finding was driven by the authors failing to include a required control variable.

Not only that, but they seemingly knew they this variable was important.

Read 13 tweets
Mar 30
Thread of natural sources of different medications.

We can thank the Gila Monster for modern GLP-1 drugs like Ozempic Image
Image
Ziconotide is a powerful non-opioid painkiller used by people who have severe chronic pain that's resistant to other forms of treatment.

It was discovered in the venom of killer Cone Snails. Image
Image
Trabectedin is a chemotherapy drug that was isolated from an extract of sea squirts. Image
Image
Read 19 tweets
Mar 30
In case it's unclear, I think the mechanism here is likely to be preferentially enlarging productive firms.

In more competitive economies, more productive firms have larger market shares🧵

America is a stand-out example of this: Image
Prior to the fall of the Iron Curtain, markets in Eastern Europe were remarkably inefficient.

After its fall, market reforms occurred, and after they took place, they went from less efficient firms capturing larger market shares to the opposite: more efficient firms dominated! Image
The thesis is this:

America's stock markets are set up in a way that, incidentally, promotes more efficient firms capturing larger market shares.

There's not yet enough data to know if this is true, but time will tell if this possibility holds up.
Read 4 tweets

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