## Thursday, February 21, 2008

### Deja Vu

What are the odds I'd get behind the exact same truck I was sitting behind last Friday? And I think it's at the exact same light.

Actually, the odds are probably higher than you'd think. Hmmm...that would be an interesting math problem.

Jim leaves work at approximately the same time as 1200 other commuters travelling in the same direction. What is the probability that he will get stuck in traffic behind the same vehicle more than once in the period of a week?

1. That is a good problem for Jud! LOL!

2. C'mon, Jud! What's the answer?

It reminds of the "birthday" problem. What's the likelihood, in a room of 25 people, that any two people will have the same birthday? It's actually over 50%. When you bump that number to around 50 people, it's over 90%.

If you're as interested in probability as I am (ok, I'm a nerd), here's a good description of the problem.

3. My favorite example of probability
is from Dumb and Dumber.

Lloyd Christmas: So what are the chances that a guy like me and a girl like you could get together?

Mary Swanson: Uhh, like one in a million.

Lloyd: So your telling me there's a chance!

I like thinking about probablity as well. Sometimes I wonder if you could derive certain probablity functions and just go out and rule Vegas-- sortof like Rain Man... JK. We should only use things of that nature in the nobel quest of benefitting humanity :)

Actually, we do get to use a little probability in our highway drainage work. We design our drainage structures to meet certain storm frequencies. Side ditches and storm sewer systems are designed for the 10 year storm, and culverts (cross drains and ditch crossings) are designed for the 50 yr storm. To find the true definition of these storms, you take the inverse of the year and that is the probability that the event could happen within the current year. For example, the probability of having a 50 yr storm this year is 1/50= 0.02, or 2%. So technically you could have a 100 yr storm followed by a 50 yr storm back to back. This can be a hard thing to explain to the public sometimes.
Sorry this was so long, I am at the hotel :)
-Jud

4. It happens to me at least 3 times a week. We just live in too small a town dude.

5. Jud - hope you're having a good trip! Hey, you're probably back now, aren't you? So, a 10-year storm is the kind of storm that might occur once in 10 years? And the probability of having it is 10%? Am I way off?

"Charlie" - but that's in Huntsville! Surely it's a lot less likely there...

6. thanks-- I had a good trip. It's always good to get back. Yes, you are correct about the 10 year storm...
-Jud

7. Actually, if you throw in an intentional tort, a drunk person, and a visit to the hospital, it could be a question on the BAR exam!!!

8. I tend to be ok at test-taking, but that scares me!