## Friday, July 16, 2010

### Politics Gets in the Way

A poll is conducted the day before a state election for senator. There are only two candidates and the poll shows that 53% of the oters surveyed favor the Green candidate, with a margin of 2.5 percentage points. Should the Green candidate plan a victory party?

1. I'm not sure about the maths involved here, but never trust a poll. I would recommend the Green candidate to wait until the results are in.

2. OK. I've been thinking about the maths, nagging at me all day. Presumably the 2.5% margin means a 95% probability that the vote will be 53% +/- 2.5%, i.e. 95% of the area under a normal curve. The thing with a normal curve is that they have long tails - just very improbable ones. So it is quite possible that the Green candidate will only get 1% of the vote for example, just very, very unlikely. Possible though, so as with my answer above, he or she should wait before they light the fireworks.

3. On the other hand, if the margin of error is 2.5 percentage points, that means that polling at 53% could represent 50.5% on the low end or 55.5% on the high end, giving him a majority no matter where he fell in the margin of error. Victory party planning should be in order.

4. The surveyed population might not be representative of the whole population. So it is still not clear if green should plan victory.

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