Saturday, November 28, 2009

Coconut Pancakes

These coconut pancakes were super easy and quite nice.

If only we'd had some coconut syrup. As it was, I made do with honey.

In the be careful what you say department

Yesterday N and B went out to buy Christmas hats and glow sticks for our upcoming march in the Kaimuki Christmas Parade with the Cub Scouts. B ended up with a hat with fake elf ears and so he was pretending to be a Christmas Elf during dinner. I told him he should be careful at the Parade because he looked so much like an elf that Santa might think he really was an elf and take him off to the North Pole.

At the parade last night then, we watched the various high school bands, the military band, the two semis for Ohana Concrete Pouring, some clowns, etc. Suddenly B rips off my and his Christmas hat and hides behind N. Apparently, Santa was coming on his fire truck and B didn't want to be taken away.

So he spent much of the time of Santa's passing cowering behind his mom so he wasn't swept off to build toys in Santa's Slave Elf factories.


Friday, November 20, 2009

Of flags and religion

Apparently, a Council of Islamic nations at the U.N. has started lobbying for >a treaty banning certain types of religious blasphemy. They clearly have in mind the old Danish cartoon from a couple years back. This flies right in the face of freedom of speech, of course, and I am opposed to it.

However, it made me think back to the old flag burning Constitutional amendment that periodically crops up. The idea is identical. Many Americans believe that the flag is such an important symbol that to defame it is a moral outrage they will not stand for. And so they will put aside freedom of speech for it.

I also disagree strongly there.

But what's interesting to me is that the U.S. flag is the only symbol in the country that is being treated this way. It's true that you often can't burn a cross, but that isn't because it is an attack on Christians. It's because of the history of cross burning and racial violence in the nation. No Star of David amendments being batted around by Jews; no figurines of Christ amendment, no Buddha statue amendment. Just the flag.

And this makes me think that, for many, patriotism (chauvinism in the original sense is even better) is their religion. I'm fairly patriotic myself. I care how people think about my nation; I want it to do good things; I have affection for my home nation; I would defend it if attacked. But love of country is nothing like love of God.

Something seems askew....

Sunday, November 15, 2009

The base rate fallacy

I had reason to look up the base rate fallacy a few minutes ago. Here's a very nice example of what it is and why it is relevant to our real lives today. This is a total copy and paste job from Wikipedia, with some corrections:

In a city with 100 terrorists and 1,000,000 non-terrorists (total population: 1,000,100), there is a surveillance camera with automatic face recognition software. If the camera sees a known terrorist, it will ring a bell with 99% probability. If the camera sees a non-terrorist, it will trigger the alarm 1% of the time. So, the failure rate of the camera is always 1%.

Suppose somebody triggers the alarm. What is the chance he/she is really a terrorist?

Someone making the base rate fallacy would incorrectly claim that the false alarm rate must be 1 in 100 because the failure rate of the device is 1 in 100, and so he/she is 99% sure to be a terrorist if the device rings. The fallacy arises from the assumption that the device failure rate and the false alarm rate are equal.

This assumption is incorrect because the camera is far more likely to encounter non-terrorists than terrorists. (Paca: This is the key sentence in the whole thing. While the machine only falsely tags 1% of the people it sees, it sees non-terrorists relentlessly and only sees an actual terrorist once in a blue moon, giving it a chance to make an error on non-terrorists a lot more often than it has a chance to make an error on a real terrorist.) The higher frequency of non-terrorists increases the false alarm rate.

Imagine that all 1,000,100 people in the city pass in front of the camera. About 99 of the 100 terrorists will trigger a ring — and so will about 10,000 of the one million non-terrorists. Therefore the camera will claim that 10,099 people are terrorists, and only 99 of them are in fact terrorists -- despite the fact that the camera only fails 1% of the time. So, the probability that a person who triggers the alarm is actually a terrorist is 99 in 10,099 (about 1/102). (Paca: So, practically, the camera is almost always wrong.)

The base rate fallacy is only fallacious when non-terrorists outnumber terrorists, or conversely. In a city with about 50% terrorists and about 50% nonterrorists, the real probability of misidentification won't be far from the failure rate of the device.

Paca: The same is true for something like a medical test as well. Image a test which examines a bit of tissue and gives a breast cancer diagnosis. The machine is well made and only makes a mistake 1% of the time. However, breast cancer only occurs in about 13% of American women. This means that a machine that only makes a mistake 1 in 100 times will still actually tag more women who do NOT have breast cancer as having breast cancer than it will tag women who actually do have breast cancer. Not because it's a poorly made machine, but because 87% of the women it sees do not have breast cancer.

If you are into the math (because I know you are), what we want to know is the probability of cancer given a positive diagnosis. This is P(Cancer | Diagnosis = Yes). The error rate of the machine is actually (simplifying) the probability of a diagnosis given cancer ( P(Diagnosis = Yes|Cancer)), i.e., when cancer is present in the tissue sample, it correctly says yes 99% of the time. These are not the same thing.

P(Cancer | Diagnosis = Yes) does NOT = P (Diagnosis = Yes | Cancer)


P (Cancer | Diagnosis = Yes) DOES EQUAL** P(Diagnosis = Yes | Cancer)*P(Cancer)

That last term, the P(Cancer) is the probability that someone has cancer regardless of any medical diagnosis or other evidence. It's called the "base rate" or "prior probability".

The base rate fallacy is also inherent in funny statistical claims such as: Did you know that 99% of murderers eat bread?! It may be true, but the base rate of any person eating bread is probably also around 99%.

Returning to the cancer diagnosis machine, let's say we have a machine that tests 1,000 American women for breast cancer. Because the overall base rate of breast cancer is approximately 13%, we know, before any tests are done, that 130 of these women will have breast cancer while 870 will not have breast cancer. (13% * 1,000 women). How will the machine do? Let's assume it's still got an error rate of only 1%. So it will falsely say that 1% of women who do not have breast cancer do in fact have breast cancer, which is 1% * 870 or 87 women. It will also get 99% of the women who really do have breast cancer or 99% * 130 = 129 women. So, it will claim that 216 women have breast cancer when only 129 actually do. 40% of its claims of breast cancer will be false positives -- despite only making the wrong actual diagnosis 1% of the time.

This is the case with a disease that's fairly common. Over 1 in 10 women are likely to get breast cancer in their lives. The problem only compounds as the disease gets more rare.

**Technically, proportional to, since I'm ignoring the denominator)

Thursday, November 12, 2009

Stop. Circle Time.

13 years ago now I finished up a Master's degree in philosophy. I was decently good at it. I was given this graduate award that almost never goes to an M.A., but only to a Ph.D. However, I decided not to apply for doctoral programs because

1) I had spent my entire life taking classes. Really had no idea what else one could do in the world. I thought it was time to pick my head up and look around a bit.

2) I was able to write papers that got an A, but I really had nothing to say. I was 22 when I got the M.A. degree and just didn't have any wisdom at all.

3) I wasn't sure that writing yet another philosophy paper would really mean much to anyone. It's a field based on logic and rhetoric, and nothing is as easily manipulated as those two things. It's easy to spend your time being clever instead of productive. If I was going to be a scholar, I wanted to have real empirical data to show that I was right or wrong with a theory. All research can spin its wheels with bad assumptions, but please give me some data. (It's easy to do meaningless work in experimental research as well, but that's another topic. Really, the take home point is that research that's good and that matters is few and far between and the fact that it ever appears at all should make you appreciate those scholars who do it even more.)

I say all this, because I am in the middle of getting materials together for a post-doc at the University of Oslo, where I would do research in... wait for it... linguistics and philosophy. I'm actually kinda qualified for this one in a way that isn't a complete stretch. And it's one of the possibilities that's more exciting than others.

Suffice it to say, it would just be freaky if I ended up spending 2 years doing philosophy again.

However, maybe I'm just applying for the job because it's freaking Oslo! I could hike me a fjord, eat me a bunch a smoked fish, stay up to midnight with the sun, and go around doing the Swedish chef voice as if I can't tell the difference between Sweden and Norway. Really, that last one makes it all worthwhile. I'm sure the Norse love being considered Swede.

My two big questions are: 1) If I get the job, do I have to wear the helmet with the little horns? and 2) If I do, can I please change my name to Hagar the Horrible?

Friday, November 06, 2009

You can't touch this

Has no screens that you can touch. Or if you touch it, it's for your own benefit, not because it does anything.

Thursday, November 05, 2009

Planet Claire

I've been enjoying this tune a lot lately.

Planet Claire