The Trickiest Tripwires in Analytics

Posted on by David Wright

1. Are my conclusions BS?

I admire this. The author found an interesting statistical anomaly and got some attention for it. Then she discovered it was actually all due to an error and published a retraction of the use of Benford’s law as a fraud detector.

2. How do I figure out causation?

Does teen pregnancy cause poverty or vice versa? Here’s Tim Taylor:

In an ideal experiment, one might want a research design in which a random sample of teenagers becomes pregnant and gives birth, and then you could track the outcomes. Of course, randomized pregnancy is an impractical research design! But here are four approaches used by clever economists to disentangle this question of cause and effect.

A within-family approach. Look at life outcomes for sisters who give birth at different ages. The result of this kind of study is “once background characteristics are controlled for, the differences are quite modest. Furthermore, even these modest differences likely overstate the costs of teen childbearing, since the sister who gives birth as a teen is likely to be “negatively” selected compared
to her sister who does not.”

Miscarriages.  Of those teens who become pregnant, some will suffer miscarriages. Compare women who are similar in measured characteristics of family background, but some of whom gave birth as teenagers while others had a miscarriage. It turns out that their life outcomes look quite similar: that is, giving birth as a teenager doesn’t appear to cause any additional decline in later life outcomes.

Age at first menstruation. Girls who menstruate earlier are at greater risk of becoming pregnant as teenagers. One can use a statistical approach to look at two groups of women who are similar in measured characteristics of family background, but where one group has a higher pregnancy rate because they began their menstrual cycle earlier. However, the life outcomes for these groups look quite similar; is not correlated with lower life outcomes: that is, a random chance of being more likely to give birth as a teenager (because of an earlier age of first menstruation) doesn’t appear to cause any additional decline in later life outcomes.

Propensity scores. Look at girls within a certain school, so that they live in more-or-less the same neighborhood. Using the available data, develop a “propensity score” that measures how likely a girl is to give birth as a teenager. Then compare the life outcomes for girls with similar propensity scores, some of whom gave birth and some of whom did not. There doesn’t seem to be a difference in life outcomes, again suggesting that giving birth as a teenager doesn’t much alter other life outcomes.

This Is Your Brain On Sports

Posted on by David Wright

My mother in law was over once while I was channel surfing and when I came to rest on a boxing match, said “Why would anyone want to watch this kind of brutality?” Sheepishly, I turned the channel.

There really is something a bit ridiculous about watching dudes punch each other in the head for fun. “But other sports are violent, too!” is usually my limp defense. Doesn’t even address the charge. If there was a way to limit the damage without really disrupting the sport, I’d support it.

BLH has a piece discussing some recent concussion research. Here’s the gist:

Preliminary results from a new brain study suggest that there might be a point of no return for some combatants. Essentially, there becomes a point where the brain can no longer repair itself and chronic traumatic encephalopathy (CTE) becomes inevitable. The symptoms of CTE include personality changes and general cognitive difficulties, much like Alzheimer’s disease.

So boxing is probably the most concussive of sports and it’s pretty easy, and accurate, to point the finger at that community first. But remember Ted Johnson, the subject of the NYT article about concussions in the NFL?

Asked for a prognosis of Mr. Johnson’s future, Dr. Cantu, the chief of neurosurgery and director of sports medicine at Emerson Hospital in Concord, Mass., said: ”Ted already shows the mild cognitive impairment that is characteristic of early Alzheimer’s disease. The majority of those symptoms relentlessly progress over time. It could be that at the time he’s in his 50s, he could have severe Alzheimer’s symptoms.”

Ted has CTE. And Sidney Crosby missing almost a whole season’s worth of hockey over two years for “concussion-like symtoms”? Here’s an important part of the research cited by this article and BLH:

As part of an ongoing study on brain health, the researchers divided 109 licensed boxers and mixed martial artists into three groups: those who had fought for less than six years, six to 12 years or more than 12 years. Their average age was about 29.

Participants underwent MRI scans to measure their brain volume and tests of their thinking and memory.

“In those that fought less than six years, we didn’t find any changes,” Bernick said. For that group, he said, “the more you fought didn’t seem to make any differences in the size of brain structure or their performance on some of the tests like reaction time.”

But for the other two groups of boxers and combat athletes, “the greater number of fights, the sizes of certain volumes of the brain were decreasing,” he said. “But, it was only in those that fought more than 12 years that we could detect the changes in performance in reaction time and processing speed.”

Concussive sports are for the young only. Most people think of athletes playing in a sport until their reactions slow, their strength wanes and they loose their speed.

The reality is that most athletes are ‘bubble’ players who only barely make their teams and retire after a season or two. Only the best of the best, who are overrepresented in our minds and on the sports pages, play until their bodies tell them to stop. And the reality for them is that the brain may be the first thing to go.

Forcing retirement from too many concussions would be a tragedy for the player and fans. Imagine if Crosby was forced to retire at age 23? Things like this will begin to happen. And rightly so.

It’s the concussion awareness era. If it’s true that the damage can be identified early enough to limit long term problems by forcing retirement then that’s what should happen.

This Week In Space Travel

Posted on by David Wright

The price of a standard flight on a Falcon 9 rocket is $54 million. We are the only launch company that publicly posts this information on our website (www.spacex.com). We have signed many legally binding contracts with both government and commercial customers for this price (or less). Because SpaceX is so vertically integrated, we know and can control the overwhelming majority of our costs. This is why I am so confident that our performance will increase and our prices will decline over time, as is the case with every other technology.

The average price of a full-up NASA Dragon cargo mission to the International Space Station is $133 million including inflation, or roughly $115m in today’s dollars, and we have a firm, fixed price contract with NASA for 12 missions. This price includes the costs of the Falcon 9 launch, the Dragon spacecraft, all operations, maintenance and overhead, and all of the work required to integrate with the Space Station. If there are cost overruns, SpaceX will cover the difference. (This concept may be foreign to some traditional government space contractors that seem to believe that cost overruns should be the responsibility of the taxpayer.)

That’s Elon Musk

And is this related?

Space exploration company Planetary Resources will be unveiled in a conference call on Tuesday, April 24th. Besides the audacious announcement, which promises to “overlay two critical sectors — space exploration and natural resources — to add trillions of dollars to the global GDP,” what makes this unique is its high-profile support group. The venture is backed by Google executives Larry Page and Eric Schmidt, director James Cameron, and politician Ross Perot’s son, among others.

Chances any of this matters for regular folk?

Quote Of The Day

Posted on by David Wright

Reproduced by hand from my dead tree copy of *What Technology Wants*:

Old world primates have full-color vision and an inferior sense of smell compared to their distant cousins the New World monkeys…

All, that is, except the howler monkey, which, in parallel to the Old World primates, has tricolor vision and a weak nose. The common ancestor to the howler and the Old World primates goes very far back, so howlers independently evolved tricolor vision. By examining the genes for full-color vision, biochemists discovered that both the howler and the Old World primates use receptors tuned to the same wavelengths, and they contain exactly the same amino acids in three key positions. Not only that, the diminished olfactory sense of both howler and apes was caused by the inhibition fo the same olfactory genes, turned off in the same order and in the same details.

Talk about complex interactions. Is it possible for humans to figure this stuff out? What happens when computers figure this sort of thing out for us?

Bonus, from the previous page:

Biologist Richard Dawkins estimates that “the eye has evolved independently between 40 and 60 times in the animal kingdom… There are only so many ways to make an eye, and life as we know it may well have found them all.

Humanity’s Greatest Challenge

Posted on by David Wright

And I don’t say that lightly.

Why haven’t we cured cancer? The short answer is that the latest uncovered Rumsfeld Unknowns are pretty scary.

Unfortunately, paraphrase a later quote from Dr. Malcolm, cancer always finds a way. Well, pretty darned close to always, anyway. If I believed that cancer always finds a way, then I would also believe that cancer research and personalized therapy are futile endeavors. I do not believe that.

Even so, the reason we haven’t cured cancer yet is because we haven’t figured out how to overcome the power of evolution. Until we figure out a way to do that, we will continue to make only incremental progress.

The Next Revolution Approaches

Posted on by David Wright

Bold headline, non?

Well, have a rummage through these links and you tell me if this is a big deal.

First the economist gives us a story about patenting and medicine (may be gated). The bottom line here is that natural laws cannot be patented though there are some loopholes…

For example, a genetic mutation can identify patients who are susceptible to a given disease or treatment. The mutation is a natural occurrence, as is the reaction to the drug. But the invention comes in connecting the dots between these elements.

Which aren’t as big as everyone thought…

Stephen Breyer, writing the court’s opinion, affirmed that Prometheus’s patents claimed a natural law and would restrict further innovation. Administering thiopurines, observing the body’s reaction and offering dosing advice did not add up to a patentable process. “Einstein could not patent his celebrated law that E=mc2”, wrote Mr Breyer. Nor could Einstein have patented the observation by “simply telling linear accelerator operators to refer to the law to determine how much energy an amount of mass has produced.”

The biotechnology industry did not expect the ruling. It is now in a minor panic. Personalised medicine inevitably includes the application of natural laws. It is unclear which applications may be patented.

The Economist doesn’t seem to come down hard on either side of this debate, even though it has been mildly skeptical of patents in the past.

Patents are tricky buggers. Have a listen to a patent skeptic, Alex Tabarrok, talk to Russ Roberts about them. Most patents and trademarks (especially) lie somewhere between trivially stupid and economically radioactive. The one kind of patents that seem to promote innovation? Ones on drugs.

Clearly we need to find a way to research these natural processes. And now that the results may well be in the public domain (I’m not a lawyer but I realize that that probably isn’t strictly, or perhaps remotely, true – just grant it to me for a minute), who’s going to pay for the data collection, analysis, etc?

Well, let’s start with the data: the same Alex Tabarrok from that excellent Econtalk interview linked above points us to a fascinating study (abstract and writeup) where a doctor did this to himself (from the writeup):

Snyder provided about 20 blood samples (about once every two months while healthy, and more frequently during periods of illness) for analysis over the course of the study. Each was analyzed with a variety of assays for tens of thousands of biological variables, generating a staggering amount of information.

…The researchers call the unprecedented analysis, which relies on collecting and analyzing billions of individual bits of data, an integrative Personal “Omics” Profile, or iPOP.

…To generate Snyder’s iPOP, he first had his complete genome sequenced at a level of accuracy that has not been achieved previously. Then, with each sample, the researchers took dozens of molecular snapshots, using a variety of different techniques, of thousands of variables and then compared them over time. The composite result was a dynamic picture of how his body responded to illness and disease — and it was a number of molecular cues that led to the discovery of his diabetes.

Ok, so a battery of tests can give us BIG DATA on our bodies just at the dawn of the age of our ability to swallow it.

Let’s pretend I know what I’m talking about and imagine the possibility of Kickstarter projects for accumulating giant biometric databases and Kaggle competitions to work out what they mean?

Now there’s a charity I’d donate to!

Big Man Theory of History ^n

Posted on by David Wright

I’m a big fan of this blog on genetics. And I admire Razib’s ambition with this post:

one has to observe that the vast majority of modern humans are not Michelangelo or a Bachs… Men such as Alexander, Napoleon, and Hitler, were possessed of peculiar charisma… As charismatic leaders they took collections of human beings, and turned them to there purpose. Individual humans became more than the sum of their parts, and for moments exhibited almost organismic levels of cohesion.

The model I have in mind then is one where the African humans faced up against their near relations, but not as one against one. Rather, under the guidance of charismatic leaders, Paleolithic megalomaniacs driven by fervid nightmares and irrational dreams, they ground through the many enemies who fought as sums of singulars as a cohesive social machine.

Interesting, I suppose. Don’t know much about this stuff, but I can’t really see why there shouldn’t be outstanding leaders among various animals.

Anyway, Razib’s real objective is to come up with some alternative to the idea that there is a clear genetic difference between Neanderthals and H. Sapiens. This was an interesting bit:

Backing up for a moment, why do we think there might be fixed differences between Neanderthals and modern humans? The argument, as outlined in books like The Dawn of Human Culture, is that H. sapiens sapiens is a very special lineage, whose protean cultural flexibility allowed it to sweep of the field of all other hominin sister lineages. The likelihood of some admixture from these “dead end” lineages aside, this rough model seems to stand the test of time. Consider that the Mousterian technology persisted for nearly 300,000 years, while the Oldowan persisted for 1 million! In contrast, our own species seems to switch and improve cultural styles much, much, faster. Behavioral modernity does point to a real phenomenon. The hypothesis of many scholars was that there was a genetic difference which allowed for modern humans to manifest language as we understand it in all its diversity and flexibility. The likelihood of this seems lower now that modern humans and Neanderthals have the same variants of FOXP2, the locus which seems to be correlated to elevated vocal and auditory capabilities across many vertebrate lineages. And, if it is correct that ~2.5% or so of modern human ancestry in Eurasia, and nearly ~10% in Papua, comes from “archaic” lineages, then I think that should reduce our estimates of how different these humans were from the Africans.

Pro Tip

Posted on by David Wright

If you’re an eater of all-natural penut butter, like I am, one of the most infuriating things in the world is having to remix the oil and solid paste that gravity pulls apart after the jar’s been sitting on the shelf for a while.

When I was a kid, I used to pull out a knife or spoon or something, shove it into the jar and churn. It spills over the top, I get all greasy… What a mess.

Well, folks, I don’t do that anymore.

NOW, I take the jar and simply plop it into the cupboard upside down and wait a day or so.

What happens? Well that infuriating separation process is thrown into reverse and gravity’s my friend now. When I pull it out again a little while later, I get smooth and consistent creamy goodness.

This isn’t perfect, of course, as there might be the odd clump hidden in there somewhere, but by the time I find it, the jar is low enough that I can dispose of the offending sludge with a quick flick of my knife.

Use this knowledge wisely, readers.