Airport Security and Statistics

"Lottery: A tax on people who are bad at math." -Unknown

The debate about profiling during airport security screening is still active today. While profiling can be an excellent way to direct limited resources in the most efficient manner, there seem to be some fundamental misunderstandings about how to do so.

Screening for potential terrorists is the most visible kind of security in the media today. In this application the question of profiling becomes, "What kind of people are most likely to be terrorists?". Unfortunately, the answer to this question has become clouded by people who badly misunderstand the fundamentals involved.

One common argument takes the form of that in an e-mail I recently received plugging the idea that many terrorists are young muslim men (YMM) so our security screeners should focus on YMM. Observe that the logic here is badly flawed: The assumption provided, that most terrorists are YMM, is exactly wrong for guiding profiling. Even if it were true that many or most terrorists were YMM, the data describe a set used to predict the chances of a person being a Muslim male given that the person is a terrorist. This is NOT the correct data to construct a profiling scheme because it is backwards: the data we want is the chance of a person being a terrorist given that the person is a YMM, not the chances of being a YMM given that a person is a terrorist. The fact that these statistics are neither interchangable, nor can be used (without other data) to predict the other is both subtle and critical to understanding the matter.

Consider a simplified version of the problem: I have a tray of 100 coins all pennies and dimes. There are 50 coins which are heads. If I tell you that all of the pennies are heads, can you tell me how many heads are pennies? No, the heads up coins could be 50 pennies or 49 dimes and one penny. The statistic you need to answer the question is the fraction of heads that are pennies. If I told you it was 50%, you would know there were exactly 25 pennies which were heads. Note further that knowing all pennies are heads is NOT the same as all heads are pennies and that in general knowing that "All X are Y" says nothing about how many Y are X.

Consider another hypo: All terrorist are beings that are alive. Are all beings that are alive terrorists? No! Not even close.

Going back to the profiling issue with this statistics matter in mind, we see that the data posited, most terrorists are YMM, does not allow us to predict the chance of a person being a terrorist given that he is a Muslim male. What a security team WOULD need is the RATIO of the chance that a person who is a Muslim male is a terrorist vs. the chance that any given person is a terrorist. Given that ratio, let's call it "X", you can assign a probability of a detailed stop and search to Muslims equal to (X)*(the probability of stopping any given party).

Since we don't know what X is nor could we predict it bsed on the assumption that most terrorists are YMM, we cannot profile YMM efficiently. Any attempt to profile on this data is a stab in the dark at best. While political correctness is not a reason to avoid profiling, the legitimate fear of profiling inefficiently such that the chance of detecting a terrorist is decreased IS a legitimate reason to avoid profiling.

One way that profiling might actually be used to make us safer is to stop screening the pilots since the X ratio for a pilot had better be zero or vanishingly close to it.

Responsibility and Leadership

"The buck stops here!" Harry S. Truman
http://www.brainyquote.com/quotes/quotes/h/harrystru162071.html

Harry Truman was one of the finest Presidents the United States ever had. The man recognized that the reponsibility of the US chief executive was awesome because he had been invested with such extensive authority. This kind of authority is a boon since it aids the executive in executing his duties per his oath of office, but it is also a burden. Vesting the executive with such authority gives him ability to respond to a given matter, but as "ability to respond" indicates, it comes with commeasurate responsibility. Truman recognized his responsibilites when he said, "The buck stops here!" That is, Truman realized that he was the ultimate authority and could not "pass the buck". When everything was said and done, he was the man behind it all. He took responsibilty for everything done on his watch like a good leader should.

In legal parliance, this is recognized as the doctine of "respondeat superior": the leader is responsible for what his subordinates do whenever they are acting as his agents. This responsibilty extends even to those actions not expressly requested or required by the agent. For example, a pizza shop owner may be responsible if his delivery driver punches a man if the delivery driver thought doing so was part of his job (say in the mistaken belief that the man was stealing the pizza).

Today we don't have this kind of leadership at the top. Our executive branch has engaged in rampant "buck passing". The intelligence upon which the executive decided to go to war was found to be flawed in many respects. While I have yet to find any explicit statement from the President claiming he was misled (by bad intelligence), the President has an affirmative duty to take responsibilty for the intelligence upon which he acts. He has not done so: instead George Tenet was allowed to "fall on his sword" and resign. By failing to stand up and explicitly take responsibilty, the President has tacitly allowed responsibilty for bad intelligence to fall on Tenet and thereby passed the buck. Herein, lies the problem: either you are a leader, in which case you are responsible for the nature of the leadership and any "misleading", or you are NOT a leader in which case you might be able to excuse your actions by claiming to have been misled. Our leader allows others to take the fall and cloaks himself in the tacit excuse that he was misled; as such he is no leader at all. Where is the leader that will stand up and say, "I did this! I deserve the credit and the blame! It was all me!"? Bush has never done this and America deserves an executive that will do so. Anything less gives us an executive and denies us a leader.

It is no surprise to me that confidence in Bush has fallen so low- Being an executive is a matter of getting the votes, being a leader is a matter of character.

Sugar is Evil

Most of the calories we consume can be attributed to one of the catagories in the set of Protein, Fat, and Carbohydrate. Protein is everyone's friend. It provides all those nice amino acids which your body uses to build more you. Eat your proteins and enjoy clear skin, strong muscles, and shiny hair. Hooray. Fat gets a bad rap. Fat is a great way to store energy, high fat foods can be excellent sources of oil soluable vitamins like A, E, and D, and high fat foods can help promote high-density cholesterol. While not every high fat food is good for you, there are many healthful foods which are very high in fat and can be included in a heathy diet.

This brings me to the last catagory: Carbohydrates. The set of compunds which are called "Carbohydrates" includes what are known as trisaccharides. Trisaccharides include cellulose and starch. These compunds provide energy to those animals capable of digesting them. Since humans and other monkeys can't digest cellulose, it really only acts as a transport agent by helping the body to push food from one end of the digestive tract to the other. There are lots of good foods which are high in both cellulose and starch and since the body does need a very small amount of them, they are a necessary evil.

This brings me to the unneccessary evils: mono and di-saccharides: glucose, fructose, galactose, sucrose, maltose, and lactose... These are the enemy. Your body doesn't really need you to consume them directly but for some reason people not only want to suck down all the high sugar foods that they can, they fill their kids up with it. It's not good for you and it never was. Moreover making heathful choices is made difficult by modern marketing: sugar is everywhere. You have to stay VERY vigilent in order to avoid it.

This Thanksgiving, do your body a favor. Enjoy all the turkey, ham, or tofu that you want, have a second helping of mashed potatoes, rice, or stuffing if you like, and say no to any dish described as a "pie", "cake", "cobbler", or "crisp". Your body will thank you.

Prima Doctrina

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