Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Pages: [1] 2
Good article from highlighting flawed statistical thinking

Here are three versions of the same story:

1. In the fall of 1996, Sally Clark, an English solicitor in Manchester, gave birth to an apparently healthy baby boy who died suddenly when he was 11 weeks old. She was still recovering from the traumatic incident when she had another baby boy the following year. Tragically, he also died, eight weeks after being born. The causes of the two children’s deaths were not readily apparent, but the police suspected they were no coincidence. Clark was arrested and charged with two counts of murder. The pediatrician Roy Meadow, inventor of the term “Munchausen Syndrome by Proxy,” testified at the trial that it was extremely unlikely that two children from an affluent family like the Clarks would die from Sudden Infant Death Syndrome (SIDS) or “cot death.” He estimated the odds were 1 in 73 million, which he colorfully compared to an 80:1 longshot winning the Grand National horse race four years in a row. Clark was convicted and sentenced to life in prison. The press reviled her as a child murderer.


The mathematical lens that allows us to see the flaw in these arguments is Bayes’ theorem. The theorem dictates that the probability we assign to a theory (Sally Clark is guilty, a patient has cancer, college students become less theistic when they stare at Rodin), in light of some observation, is proportional both to the conditional probability of the observation assuming the theory is true, and to the prior probability we gave the theory before making the observation. When two theories compete, one may make the observation much more probable, that is, produce a higher conditional probability. But according to Bayes’ rule, we might still consider that explanation unlikely if we gave it a low probability of being true from the start.

So, the missing ingredient in all three examples is the prior probability for the various hypotheses. In the case of Sally Clark, the prosecution’s theory was she had murdered her children, itself an extremely rare event. Suppose, for argument’s sake, by tallying up historical murder records, we arrived at prior odds of 100 million to 1 for any particular mother like her to commit double infanticide. That would have balanced the extreme unlikelihood of the observation (two infants dying) under the alternative hypothesis that they were well cared for. Numerically, Bayes’ theorem would tell us to compare:

(1/73,000,000) * (99,999,999/100,000,000)  vs. (1) * (1/100,000,000)

We’d conclude, based on these priors and no additional evidence aside from the children’s deaths, that it was actually about 58 percent likely Clark was innocent.

The problem, though, is the dominant mode of statistical analysis these days isn’t Bayesian. Since the 1920s, the standard approach to judging scientific theories has been significance testing, made popular by the statistician Ronald Fisher. Fisher’s methods and their latter-day spinoffs are now the lingua franca of scientific data analysis. In particular, Google Scholar currently returns 2.85 million citations including the phrase “statistically significant.” Fisher claimed signficance testing was a universal tool for scientific inference, “common to all experimentation,” a claim that seems borne out by its widespread use across all disciplines.

And this part in particular will likely make me even more unpopular on this forum
Just a few of the other casualties of replication include:

  • The study in 1988 by Strack, Martin, and Stepper on the “facial feedback hypothesis:” when people are forced to smile, say by holding a pen between their teeth, it raises their feeling of happiness.
  • The 1996 result of Bargh, Chen, and Burrows in “social priming,” claiming, for example, when people are exposed to words related to aging, they adopt stereotypically elderly behavior.
  • Harvard Business School professor Amy Cuddy’s 2010 study of “power posing:” the idea that adopting a powerful posture for a couple of minutes can change your life for the better by affecting your hormone levels and risk tolerances

I haven't even read the article yet, just wanted to share based on that picture of a machine that looks like something straight out of a hard sci-fi novel. And it's even called the HADES detector ffs.

Various innovations in the field of genomics over the past few decades have given researchers hope that resolutions to long-lasting debates might finally be on the horizon. In particular, many have become optimistic about the prospects for disentangling the threads of “nature” and “nurture” — that is, about determining the extent to which genes alone can explain differences within and between populations.

But two recent studies are now calling some of the methods underlying those aspirations into question.

A key breakthrough was the recent development of genome-wide association studies (GWAS, commonly pronounced “gee-wahs”). The genetics of simple traits can often be deduced from pedigrees, and people have been using that approach for millennia to selectively breed vegetables that taste better and cows that produce more milk. But many traits are not the result of a handful of genes that have clear, strong effects; rather, they are the product of tens of thousands of weaker genetic signals, often found in noncoding DNA. When it comes to those kinds of features — the ones that scientists are most interested in, from height, to blood pressure, to predispositions for schizophrenia — a problem arises. Although environmental factors can be controlled in agricultural settings so as not to confound the search for genetic influences, it’s not so straightforward to extricate the two in humans.

Given that some experts want to roll out polygenic scores in the clinic, it’s already clear that this flaw could deepen the disparity in health care. In a study published last month, researchers found that trying to translate insights gleaned from European data to make health predictions in people of African descent led to as much as a 4.5-fold drop in accuracy. Others have tried using polygenic scores to make poorly supported claims about differences in behavioral and social traits between populations (such as IQ and education attainment, which are far more difficult to define and unpack than height is, yet are being used to potentially inform future policymaking decisions). “It’s kind of scary,” said Sarah Tishkoff, a geneticist at the University of Pennsylvania who emphasized how critical it is to collect more underrepresented genomic information.

Philosophy & Science / Another galaxy without dark matter
« on: April 03, 2019, 11:25:11 pm »
It always spooks me a little to read about astronomy, but at the same time it intrigues me despite me knowing nothing about it. In a different timeline, perhaps I'd too be an astronomer... It makes me feel a little jealous.
Anyway, it's further evidence that dark matter is a real thing, however dark it might be.

General Misc. / 'How the Brain Creates a Timeline of the Past'
« on: February 14, 2019, 01:15:40 am »
This article at quanta might of interest to some of you here.

The Almanac: PON Edition / ARC: TWP Chapter 2
« on: August 23, 2018, 10:39:52 pm »
Images, stark and dry, of the Steppe assailed him. The other women tearing at his mother's hair, clawing at her face, clubbing her with rocks, stabbing her with sticks. Mother. A bawling infant hoisted from her yaksh, tossed into the all-cleansing fire--his blond-haired half-brother. The stone faces of the men turning away from his look . . .

From TDTCB chapter 12:
Then, two seasons later, the other women strangled his mother for giving birth to a blonde girl. As they raised her corpse on the vulture poles, he began to understand what had actually happened.

Can anybody explain this?

Philosophy & Science / Axolotl genome sequenced
« on: July 07, 2018, 12:15:43 am »

Regarding the Neanderthal discussion we had a couple of days ago. This magazine is just awesome in general, thanks Madness or whoever it was for showing it to me.

A talk by Nima Arkani-Hamed about the same thing discussed in those talks I linked to in my other thread. This one seems to be a bit easier to understand for laymen:

Philosophy & Science / Somatic growth, aging, and longevity
« on: January 17, 2018, 03:38:05 am »
Rejoice fellow manlets, for God has let us drink deeper from the chalice of life:

Philosophy & Science / How to see a memory
« on: January 14, 2018, 01:42:07 am »
I guess the best way to post these is to make a thread for each one. Thought some of you guys might be interested in this

Philosophy & Science / Random interesting science related stuff
« on: January 10, 2018, 08:15:29 pm »
This is a thread for random interesting science related stuff.
I'll start off:
This is physics talk I'm watching right now. It's about the fine tuning of the universe. It's not too hard to follow the broad ideas for a layman. Link: Why is there a Macroscopic Universe? (Nima Arkani-Hamed)

This is a cool little video where they hooked some heart cells to some gelatine/gold-ray thingy.
Robotic ray is part animal, part machine

Brian Cocks talks a little bit about heat death. It's very poetic and there's one line in particular that moves me near the end.
Death of the Universe

Some creepy illusion stuff

Synchronized oscillations of a synthetic quorum clock in bacteria.
The related article is behinid a pay wall but there's an article describing the article here.

Philosophy & Science / Gods as Topological Invariants
« on: December 20, 2017, 11:11:04 pm »

Philosophy & Science / What do you believe? (Redux)
« on: November 13, 2017, 03:23:32 pm »
I believe that there is a God, in a very trivial and general sense. And free will is trivially false.

Life (capital L) as we know it is basically a system that works towards two things: increased complexity (intelligence) and decreased chaos (entropy).
Entropy will always increase for an isolated system.
In that sense, life is not ontologically different from the rest of matter. Free energy goes in, the system consumes to maintain a steady state, heat comes out.
What is special about is that we are configurations of matter aware of ourselves and the universe. I would love to live long enough to see how it all ends.

Pages: [1] 2