Let me say publicly that DonBoy’s answer exudes a combination of intuitive genius and confidence that make me think DonBoy is going to do big things in his life. -- Steven D. Levitt (Freakonomics blog)
Tuesday, April 22, 2008
You Can't Trust Anyone Nowadays


Al-Qaida No. 2 says 9/11 theory propagated by Iran

Osama bin Laden's chief deputy in an audiotape Tuesday accused Shiite Iran of trying to discredit the Sunni al-Qaida terror network by spreading the conspiracy theory that Israel was behind the Sept. 11 attacks.
"The purpose of this lie is clear -- (to suggest) that there are no heroes among the Sunnis who can hurt America as no else did in history. Iranian media snapped up this lie and repeated it," he said.

Friday, April 11, 2008
Nine is Prime, Nine is Prime, Nine is Prime

Convincing un-math from a Slashdot poster!

I read one of Marilyn Vos Savant's books, and in it she listed 9 as a prime...

But there's a more-than-50% chance that 9 is prime!

I test primeness by dividing the test-number by all integers, from 2 through the test-number's square root, looking for a zero remainder. So, first, I divided 9 by 2. I worked on this for a while, and ended up with a nonzero remainder. So far, 9 looks prime, and I've already tested half of the potential divisors! In fact, there's just one more potential divisor to try: the number 3. I'm almost done, and everything rides on this final calculation. There's a lot of uncertainty here.

What are the chances that 9 is just going to happen to be divisible by the very last potential divisor that I try? I'll grant you that the chances are non-zero; there really are some composite numbers out there. But the chances aren't one, either. For example, when I was testing 17 for primeness, the last potential divisor I tried was 4, and it didn't work. This last calculation could go either way.

So here we are, having tested half of the possible divisors, and so far 9 is looking prime and there's just one more divisor to test against. So, I ask you: do you want to bet 9's primeness/compositeness on this last calculation? I'll make it easier for you: I tell you right now, that 9 is just like 17, in that it is not divisible by 4. And then, I'll even give you an option: we can finish the calculation by dividing 9 by 3, or you can change your candidate divisor to 5, now that you know 4 doesn't work. Well.. what'll it be?

Saturday, April 05, 2008
Truth in Advertising

Here's a screen grab from a commercial for the current #1 movie, "21", about the MIT students who won a lot at blackjack.

The voice-over confirms it: "Entertainment Weekly raves: 'A Card-Sharp Thriller!' "

That's true. The review is even fairly positive. But as you'd see at the link, "Card-Sharp Thriller" is -- obviously -- a purely descriptive term, like "War Movie!" Nevertheless, with the word "sharp" in there, it sure sounds like a compliment, doesn't it?

Related: Even the book that the movie is a blurry copy of isn't mostly true.

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