A minor point here, but relevant since the OP is emphasizing the importance of understanding the Poisson distribution - if the mean really was 10,000, any obser

A minor point here, but relevant since the OP is emphasizing the importance of understanding the Poisson distribution - if the mean really was 10,000, any observation outside the range [9,500, 10,500] would be extremely unlikely. http://en.wikipedia.org/wiki/Poisson_distribution http://en.wikipedia.org/wiki/Poisson_distribution