[BruceZ]

[ QUOTE ]
I was under the impression that Amarillo Slim performed this bet with 30 people, not 25. I think this increases the odds to about %72.

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70.6%, assuming 365 equally likely b-days.

Here are some other stats:

mean: 24.6
median: 23
mode: 20

The mean is the expected value, or the arithmetic average of the number of people it takes to get a match if we repeated this experiment over and over with different people. The median is the number of people it takes to get a match 50% of the time (actually 50.7% here). The mode is the most likely number of people it takes to get a match, or the most common number that results in a match.