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November 02, 2010

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Xi'an didn't say 8 percent, he said 8 per mil. It's a once in a century event for that lottery, not a once every dozen years.

Thanks djm. My error: I read, "However, if we start from the early 2009, the probability of no coincidence goes down to 0.992, which means there is close to an 8‰ chance of seeing twice the same outcome since the creation of this lottery.", but missed it was a ‰ symbol, not a % symbol. Thanks for pointing out my error, which given the topic of this post, was an embarrassing one!

a> the incident of six numbers repeating themselves within a month is an event of once in 10,000 years
b> there's actually about an 8 in 1000 chance of this having occurred in the two years the Israeli lottery has been run under these rules.

How does (b) contradict (a)? If I understand (b) correctly, there is a 8 in 1000 chance of "six numbers repeating themselves" in a twenty-months period (since the creation of the lottery), but it says nothing about the probability of an event of the type "six numbers repeating themselves _within_a_month_".

Actually I do not see any contradiction,
see
http://freakonometrics.blog.free.fr/index.php?post/2010/11/02/Comments-on-probabilities

Apologies to everyone for using the "\permil" symbol that confused readers.... I also added a computation to my post to answer a question similar to carlito's.

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