Posted on May 20, 2010 at 1:55 AM |

** birds** : Nothing much to report, despite the conditions this morning that looked pretty good for migrants, I only had a single

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*male Stonechat, Pleinmont*

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*the strange stance of this second bird was because it was watching a GBB Gull overhead.*

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** nonsense** : I was reading on the internet the other day about mathematical probability (as I'm sure everyone does on a regular basis) and came across something which I found pretty amazing called the "

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When you first hear this figure you think that it can't be right, it can't be so low surely. So I checked the registers of the first 8 form groups in our school, since pupils in a form are not at all chosen by birthday so it is quite (but not perfectly) random. There are between 22 and 27 pupils in these forms so according to the birthday paradox, four of these forms should have a pair of pupils with the same birthday. In fact 5 out of 8 classes had a birthday match - so it works!

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The mathematics of this are actually quite complex but it can easily be proved to be true. To simplify a lot, if you meet someone in the street there is 1 in 365 chance they have the same birthday, very low. But if you consider this problem as comparing pairs of people, in a room of 23, there are actually 253 pairs. This is well over half of 365, so there is a reasonable chance that there will be a match in these pairs. Of course this is not a true paradox but an "intuitive" paradox, because it is so unexpected that the answer is so low.

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My favourite paradox is what will happen when Pinnochio says *"my nose will grow now!"*?

Categories: 2010 Spring