Sunday, November 23, 2014

Shooting at Florida State University

On Thursday morning, I woke up groggy in a hotel room in Atlanta, after my phone buzzed for the third time. It was 6am, and I was at the AIChE annual meeting.

In a few minutes, I found out about the shooting at Strozier Library on campus.

Shortly after midnight, a gunman, later identified as Myron May, had opened fire and injured three unsuspecting students, whose only fault was that they were in the wrong place at the wrong time. The library had been unusually packed, due to exams and project deadlines that mark a semester rolling to its end.

Obviously, this one struck really close. I stroll past Strozier library and Landis Green almost daily, because it is one of the most beautiful parts of the campus.

Even as the University is struggling to make peace with this senseless random act, a cloud of confusion envelops me.

Personally, I am firmly anti-gun. There are a few things, I am absolutely clear about: (i) assault style rifles have no place in a civilized society, (ii) some background checks/licensing are absolutely needed to prevent criminals and psychotics from picking up a gun from the nearest Walmart.

An outright national ban on guns would probably please me, but it is politically difficult. I also haven't sorted out this issue in my mind completely, and a number of discussions I've had with friends and colleagues have left me with a lot of nuance.

For example, I recently heard the argument that gun laws should be local: the rules in downtown New York City need not be the same as the rules in a rural Minnesota village, where hunting is woven into the fabric of the society. At face value, this certainly seems to be a reasonable proposition. Furthermore, banning firearms from a jurisdiction is probably not going to deter a criminal, who is bent on breaking the law in any case. Background checks can help, but someone could buy a weapon when they are sane, and retain the weapon, unless gun licenses are renewed annually.

But perhaps, the issue gnawing at me most uncomfortably is whether all this talk about banning guns lets us avoid looking at the issue of serious mental illness. In all of the recent school and campus shootings, guns and mental illness have co-conspired to create a deadly cocktail. Guns seem like an issue that can be divided into a neat binary position - you have them or you don't.

Mental illness, on the other hand, is a much more complicated. It is already stigmatized, and a part of me worries that when the spotlight is turned towards the issue, people will say "put all these loonies away", or "snatch away their guns", rather than having a honest discussion of how to restructure community and safety nets so that mentally ill people can get the help they deserve.

In summary, there are a few things I feel certain about. I would rather see "passionate incrementalism" (a phrase I learned recently and have grown to love) to move the issue forward in little steps, rather than attempting impossibly large leaps that circle us back to the beginning.

Wednesday, November 19, 2014

Longform Articles

1. The Empire of Edge: How  a doctor, a trader, and the billionaire Steven A. Cohen got entangled in a vast financial scandal. (New Yorker)

2. The Empire Reboots: Can CEO Satya Nadella save Microsoft? (Vanity Fair)

3. Beyond the Bell Curve: A beautiful exposition of the mystery of a universal statistical law. (Simons Foundation)

Sunday, November 9, 2014

New Links

1. A short history of important equations including the ideal gas law, Fourier transforms, and the wave equation (the Guardian)

2. The experiment Galileo would have loved to see:

Or perhaps not!

3. The problem with Nate Silver (Matt Yglesias)

4. An interesting puzzle (Michael Lugo): Given 5 digits construct a three digit and a two digit number so that the product is maximized.

Friday, November 7, 2014

Screening for Down's Syndrome

In our discussion on Bayes theorem in the seminar yesterday, I brought up a personal anecdote. During my wife's first pregnancy, she was offered the choice of taking an integrated test to screen for Down's syndrome in the fetus.

I looked up the numbers for the accuracy and false positive rates and found that they were about 95% and 5% respectively (somewhat of a coincidence that these numbers add up to 100%).

The baseline rate of the syndrome steadily increases with the age of the mother.

For a 25 year old mother, it is 0.0001 (1/1100).
For a 35 year old mother it is 0.004 (1/250).
For a 45 year old mother it is 0.05 (1/20).

You can run these numbers through one of the online calculators I wrote about yesterday.

If the test is positive, then the posterior probabilities are again a function of age:

For a 25 year old mother, it is 1.7%.
For a 35 year old mother it is 7.1%.
For a 45 year old mother it is 50%.

Thus, at that time I concluded that the taking the test would only have been meaningful if my spouse were around 45 years old.

For young mothers, even a positive test result is not of particularly great practical value.

Wednesday, November 5, 2014

Bayes Theorem: Interactive Modules

In our undergrad seminar, we have been reading about Bayes Theorem from a very nice post by Eliezer Yudkowsky. However, most of the Java applets on the page don't seem to work (or at least I couldn't not get them to work!).

Fortunately, thanks to Geogebra, there are multiple interactive HTML5 "applets" which work straight away in any modern browser. If you have Geogebra on your system, you can download and modify the applet as well.

Here is a link to "Exploring Bayes' Theorem"

If you like "tree" based descriptions better, here is another applet/worksheet.

Tuesday, November 4, 2014

Wason Selection Test

I learned about this interesting logic puzzle yesterday. Here's how wikipedia poses it:
You are shown a set of four cards placed on a table, each of which has a number on one side and a colored patch on the other side. The visible faces of the cards show 3, 8, red and brown. Which two cards must you turn over in order to test the truth of the proposition that if a card shows an even number on one face, then its opposite face is red?
 Apparently 90% of the people fail.

The same article goes on to mention that given the right social context most people make the correct choice.
For example, if the rule used is "If you are drinking alcohol then you must be over 18", and the cards have an age on one side and beverage on the other, e.g., "16", "drinking beer", "25", "drinking coke", most people have no difficulty in selecting the correct cards...