Saturday, July 03, 2010

Lies, Gender, and Damned Statistics

On Slashdot recently I encountered another version of Martin Gardner's two-children puzzle. The original problem is this:
I have two children. One of them is a boy. What are the odds the other one is also a boy?
If you're a human living in the world, three things are probably true of you vis-a-vis this puzzle. 1) You've heard it before, 2) you got it wrong the first time you heard it, and 3) the correct answer still seems wrong to you.

The correct answer, if you've never encountered it, is based on the following a priori: there are four equally-likely ways to have two children:
  • a boy followed by a girl
  • a boy followed by another boy
  • a girl followed by a boy
  • a girl followed by another girl
You look at that graph, you find all of the rows where both children are boys (1), and divide it by the number of rows where at least one of the children is a boy(3), and you get the answer: 1 in 3.

Mrs. Transient Gadfly will tell you that Mr. Transient Gadfly's position on all questions of this nature is that it is not a math question, it is a language question. And, moreover, it is an ill-posed one. The nature of how poorly this question is posed is laid bare by the variation linked above:
"I have two children, one of whom is a boy born on a Tuesday. What's the probability that my other child is a boy?"
If you follow the logic of the original problem (which, being that I am a human in whose true nature you will find the compunction to write this blog, I did) you'll write out all the days of the week your first child could be born, followed by all the days of the week your second child could be born, look at all of those that have a boy born on a Tuesday in them, count the number of those that have a second boy, and come up with the answer (it's 13 in 27, if you write out the table. Do not write out the table). If you are literally anyone else in the world, you will come up with a much better answer: 1 in 2. The crux of the issue, which the linked article almost hits on but then fails to, is that there is no universe in which the given answer (13 in 27) is correct. It would require the asker of the question to randomly chose a day of the week and a gender, and then only pose the question if he or she had a child that matched those criteria.

(Here is one of those moments where Transient Gadfly has an existential crisis about the nature and purpose of The Odds Are One: should I explain why what I just said is true? It would take, like, seven paragraphs and still nobody reading would understand the logic. I'm not going to do it this time. You'll just have to take my word on this one).

If you're anyone else, you look at that question and understand the only way someone would pose the question: he or she randomly chose one of his or her children, and listed two characteristics of that child: his gender, and the day of the week of his birth. And you will come up with the correct answer to the question, because when you randomly chose one of your two children, the gender of the other one is a coin-flip. So, you might well ask, what is the difference between the original question posed by Martin Gardner and the question involving the day of the week? And the answer is, absolutely nothing. There is no way to tell, from the way it is stated, whether the asker, a parent of exactly two children, randomly chose one of his progeny and told you his gender, or a parent of exactly two children, of whom at least one is a boy, told you that fact. And it matters, because in the former case it's a 50% shot that the other child is a boy, and in the latter it's a 33% chance.

I leave you with a link to an XKCD cartoon, because it's literally impossible to make this point better than he has here.

Tuesday, June 01, 2010

New Releases

Two new releases for your Tuesday:
  • A new five song e.p. from The Calculus Affair. It's available for free download from (this link expires in two weeks, so if for some reason you're reading this after the 14th of June and you want a copy, leave me a comment or something). It's culled from my 2010 RPM Challenge album, and it's a little bit on the weird side for The Calculus Affair. But it's still pretty good.
  • My nephew, Alex Dean Trendler, arrived this morning at 6:12 a.m. MDT. 6 lbs. 1 oz., 21 1/2 inches. A big fan of The Calculus Affair, no doubt.

Wednesday, April 28, 2010

And The Worst Part Is, I Never Learned How To Read

I just got my first pair of reading glasses. My left eye doesn't quite make it around to the thing I'm focusing on, which causes me to work harder to make a reasonable stereo image of something close to my face (this condition has a name, but I can't remember what it was). I've apparently been compensating for this problem without really knowing I had it. At the beginning of my last visit my optometrist did a couple of checks and then asked: Do you find it difficult to focus, or that sometimes you see a double image when you read? Do you get tired while reading? Yep. All my life. I'd never really noticed the first thing until Mrs. Transient Gadfly pointed out that I close one eye when reading in bed, which was apparently my main compensation mechanism (it works only passingly well, as I fall asleep almost comically fast while reading anyway).

So now I have glasses with a slight prism in the left lens (the other option was 12 weeks of vision therapy, which I'll probably try some day when I don't have an 18-month-old). The other thing my optometrist mentioned, almost in passing, was that this would help my reading comprehension. As long as it has mattered (a little bit in high school, mostly in college), I've known that I don't absorb anything by reading it. I can follow a narrative, but my reading comprehension is for crap. I have adapted to this fine in life; on the verbal portion of standardized tests I read the questions before reading the paragraph; I figured out that I have to write down notes on the material if I want to know anything about it when I'm done.

Are these two things related? I haven't had the glasses long enough to know if they're going to help me glean new meaning from the text. But I'd always assumed that my brain just wasn't wired to learn by reading, never once thinking that it might be because my eyes were draining all my battery power just trying to stay focused on the words in front of them.