On Wed, 4 May 2005 [EMAIL PROTECTED] wrote:
It seems to me that the line in the function
if (n > classes) return(1)
is only relevant to the default case of coincident = 2. (Naturally, if there are more people than classes, then at least one class must contain 2 people).
Yep, looks like a bug to me. Thanks.
I do note that the approximation used in pbirthday is not very good for small n, so fixing this bug still doesn't give the right answer for your example. For small n the best solution is simulation or direct calculation. The point of the pbirthday approximation is that the untrained intuition guesses the probability to be about
n(1/classes)^(coincident-1) and the approximation is usually quite good when this is much smaller than the true probability.
-thomas
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