Thursday, September 18, 2008

What are the odds?

It's abundantly clear that most people in and out of the media don't understand probability. Those that do tend to take advantage of that weakness to "lie with statistics."

"X doubles cancer risk!" (from 1 per million to 2 per million) - pretty scary stuff, eh?

It works the other way too. This story tells of as unlikely a coincidence as I can imagine but doesn't even mention its improbability. To anyone who can do simple math, it reeks of tampering. A democratic call center in NJ had its number incorrectly entered in the phone book. By one of those coincidences that just seem to happen over and over, the number in the book just happened to be that of a sex chat line.

OK. Stay with me a minute while I try to keep it simple. Let the number of phone numbers in the book be N. Let the number of wrong numbers in the book be W. Let the number of sex chat lines in the area be S. The odds of getting your number printed wrong is W/N. The odds of a random number being a sex chat line is S/N. The odds of YOUR number being misprinted as a sex chat line is (W/N) x (S/N). Lets say there are 100,000 numbers in the book. Let's be really generous (to the argument, not to the proofreaders!) and say this is an appallingly badly proofed book and 1 in 1000 (.1%) are wrong. Now lets say there are also as many as 500 (.5%) sex chat lines in the book (this is New Jersey after all). So the odds of any number being misprinted as a sex chat line is .5% x .1% or .0005%. That means that there would be a 1 in 2000 chance of this particular circumstance happening somewhere in the book.

But it's not that simple. I'd be willing to bet that more than 99% of wrong numbers involve a simple transposition of two digits (23 => 32) or a single wrong digit. It took three digits to change the dem's phone to the chat line number. Now we're at something on the order of 1 in 200,000. Can you say "a little unlikely?" Yet the media just report on it as an amusing oddity without even the hint of foul play.

I'm not suggesting that any of these numbers or percentages are anywhere close to accurate. Someone with more time on their hands than me might want to find out the true numbers. All I'm saying is that it's more than a little (?) suspicious that such a transposition took place here. And let's be honest: it would hardly be the first time someone in the Republican party had played a little fast and loose with the phones of the opposition.

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